And a special shout out to all those who dressed up to celebrate...
Physics A and B Blocks enjoyed their Chapter 4 exam and will start with work and energy tomorrow. For your homework, remember that I am looking for how you use the terms work, power and energy, not how a scientist might use them. We'll add that part in class, but take time to think about what meaning or meanings you give those words. We'll share ideas tomorrow before starting in on work.
Introductory Physics reviewed their acceleration due to gravity and air resistance labs. We also took time to review the protocol for writing the lab synopsis and how to properly script a solid conclusion section. We then hopped into Newton's 3rd Law of Motion to conclude our discussion of good ol' Isaac (for now). Do your best not to succumb to the pitfalls of interpreting N-3. N-3 talks about the forces that arise during interactions, not the results for the objects in the interactions. That's N-2's job. The forces arise simultaneously, despite the time-lag implications of the term action-reaction forces. Lastly, the equal and opposite forces act on different objects and, therefore, are not the forces we talk about in a discussion concerning equilibrium. We'll review Newton's laws and our ideas about free fall/gravity in preparation for Friday's quiz. That quiz will center on the math of this section of work, so be prepared to button-punch that calculator!
Honors Physics went over their work on power, then turned to a review for tomorrow's Chapter 5 exam. On Friday, we'll start in on momentum and conservation of momentum. We won't be leaving the idea of forces and energy, so keep those topics in an easily accessible room in your mind palace.
10/31/12
10/30/12
The Aftermath
Well, there really is no aftermath. The storm was fairly lackluster for this part of the world, so we are back to normal.
Physics A and B reviewed for tomorrow's exam for Chapter 4. Remember to look at the videos posted a few days ago for problem-solving information for forces on objects on horizontal surfaces and on inclines. Starting Thursday - Work and Energy.
Honors Physics reviewed Friday's homework problems, then turned attention to power. Remember that power measures the rate at which work is done or energy is converted/used. Two machines with different power ratings can do exactly the same amount of work. The difference is that the higher-power machine will do the work in a shorter time period. Calculating power can take a variety of pathways - using work and time; using energy (KE or PE) and time; using net force and velocity. So, read problems carefully to plan a strategy to use power relationships. Tomorrow, review for the Chapter 5 Test, Thursday is the Chapter 5 test and Friday finds us entering the domain of momentum.
Introductory Physics conducted two lab investigations today. One looked at measuring the value for acceleration due to gravity, which we accept as 9.81 m/s2 as an average. Because the value is an average, we don't expect classroom values to necessarily fall directly on that value and, although it is minimal, there is the impact of air resistance to consider. The second lab looked at air resistance specifically, and how it influenced the motion of an object as it fell. We'll go over these labs tomorrow, but the write-ups aren't due until Friday. Tomorrow, we'll tidy last minute issues for free fall and projectile motion and move on to Newton's 3rd law of motion.
Physics A and B reviewed for tomorrow's exam for Chapter 4. Remember to look at the videos posted a few days ago for problem-solving information for forces on objects on horizontal surfaces and on inclines. Starting Thursday - Work and Energy.
Honors Physics reviewed Friday's homework problems, then turned attention to power. Remember that power measures the rate at which work is done or energy is converted/used. Two machines with different power ratings can do exactly the same amount of work. The difference is that the higher-power machine will do the work in a shorter time period. Calculating power can take a variety of pathways - using work and time; using energy (KE or PE) and time; using net force and velocity. So, read problems carefully to plan a strategy to use power relationships. Tomorrow, review for the Chapter 5 Test, Thursday is the Chapter 5 test and Friday finds us entering the domain of momentum.
Introductory Physics conducted two lab investigations today. One looked at measuring the value for acceleration due to gravity, which we accept as 9.81 m/s2 as an average. Because the value is an average, we don't expect classroom values to necessarily fall directly on that value and, although it is minimal, there is the impact of air resistance to consider. The second lab looked at air resistance specifically, and how it influenced the motion of an object as it fell. We'll go over these labs tomorrow, but the write-ups aren't due until Friday. Tomorrow, we'll tidy last minute issues for free fall and projectile motion and move on to Newton's 3rd law of motion.
10/29/12
Needless to Say...
...all exams have been pushed back one day since we are not in school today. I'm still waiting for something to warrant all of this fuss, but perhaps I'm just jaded.
Growing up in Louisiana makes me a little hard to please in terms of storms. I've endured enough full-swing hurricanes, tropical storms and tornadoes that things have to get pretty bad to make a blip on my radar. That doesn't mean I don't approach things rationally, though. I never buy or rent a residence that has electric heat, and electric stove or an electric hot water heater. We lost power frequently when I was a kid and having the ability to stay warm, have a hot meal and shower was always a blessing. When the storm warnings hit, I dig out my battery-powered radio, flashlights, candles and old-fashioned phone. Knowing I'll have some light to read, the ability to listen to music and news and make phone calls in the event of an emergency is a good thing. I also make sure all electronic devices are fully charged and my back-up power supplies are also charged to the brim. Fresh water is hoarded, dog food is stockpiled and then there's coffee. Growing up, there was no Mr. Coffee or Keurig machines. Coffee was made in a coffee pot, set in a pot of water on the stove. I still have that equipment stashed away, ready to be put to use when power fails. All possible projectiles such as garbage cans and bird feeders have been stowed and all clothes and dishes have been washed, in case that ability is lost for a few days. Yeah, the storm isn't worrying me, but I'd rather put a little effort into hedging my bets than a lot of effort trying to keep body and soul together if I've misread Mother Nature.
Stay safe and, hopefully, I'll see everyone tomorrow!
Growing up in Louisiana makes me a little hard to please in terms of storms. I've endured enough full-swing hurricanes, tropical storms and tornadoes that things have to get pretty bad to make a blip on my radar. That doesn't mean I don't approach things rationally, though. I never buy or rent a residence that has electric heat, and electric stove or an electric hot water heater. We lost power frequently when I was a kid and having the ability to stay warm, have a hot meal and shower was always a blessing. When the storm warnings hit, I dig out my battery-powered radio, flashlights, candles and old-fashioned phone. Knowing I'll have some light to read, the ability to listen to music and news and make phone calls in the event of an emergency is a good thing. I also make sure all electronic devices are fully charged and my back-up power supplies are also charged to the brim. Fresh water is hoarded, dog food is stockpiled and then there's coffee. Growing up, there was no Mr. Coffee or Keurig machines. Coffee was made in a coffee pot, set in a pot of water on the stove. I still have that equipment stashed away, ready to be put to use when power fails. All possible projectiles such as garbage cans and bird feeders have been stowed and all clothes and dishes have been washed, in case that ability is lost for a few days. Yeah, the storm isn't worrying me, but I'd rather put a little effort into hedging my bets than a lot of effort trying to keep body and soul together if I've misread Mother Nature.
Stay safe and, hopefully, I'll see everyone tomorrow!
10/28/12
Videos
Physics A and B have a test Tuesday that focuses on forces. Here's a couple of videos about the topics we've been hitting the past couple of days...
10/26/12
A Taste of Spring
...or springs, in the case of Honors Physics. Today's warm temps made staying inside and actually being school-y very difficult, but folks diligently conducted their lab investigations on energy conversions and conservation of energy. The Ball Toss lab demonstrated the conversion between kinetic and gravitational potential energies and the Energy of Simple Harmonic Motion lab tracked transformation between kinetic and elastic potential energies. The graphs very nicely showed that when one form of energy decreased, the other form increased by an equal amount, keeping the total amount of mechanical energy constant. We'll go over the lab on Monday, as well as the homework problems for conservation of energy before taking on the topic of power.
Physics A had a discussion about friction during today's class period. The origin of frictional forces was described, with static and kinetic friction being contrasted in terms of role in motion and magnitude. The coefficient of friction was introduced as a way of evaluating the role of surface materials in determining frictional resistance and the calculation of frictional force and net force was practiced in class. This latter bit was the focus of Physics B's work and we made our way through a variety of problems showing how to integrate friction into problems involving the motion of objects. Monday is general review day, so come with questions, and the Chapter 4 exam still falls on Tuesday. On Wednesday - Work and Energy!
Introductory Physics folks spent the period discussing projectile motion. We defined projectile motion, differentiated between situations where objects were and were not moving as projectiles, explored the general features of projectile motion and practice problems solving for aspects of the motion of horizontally-launched projectiles. We'll review this on Monday, before turning attention to the last of Newton's laws of motion - Newton's Third.
Physics A had a discussion about friction during today's class period. The origin of frictional forces was described, with static and kinetic friction being contrasted in terms of role in motion and magnitude. The coefficient of friction was introduced as a way of evaluating the role of surface materials in determining frictional resistance and the calculation of frictional force and net force was practiced in class. This latter bit was the focus of Physics B's work and we made our way through a variety of problems showing how to integrate friction into problems involving the motion of objects. Monday is general review day, so come with questions, and the Chapter 4 exam still falls on Tuesday. On Wednesday - Work and Energy!
Introductory Physics folks spent the period discussing projectile motion. We defined projectile motion, differentiated between situations where objects were and were not moving as projectiles, explored the general features of projectile motion and practice problems solving for aspects of the motion of horizontally-launched projectiles. We'll review this on Monday, before turning attention to the last of Newton's laws of motion - Newton's Third.
10/25/12
Forces Abound
Physics A worked on a lab that targeted Newton's 2nd law of motion. We looked at how varying force (with mass constant) and mass (with force constant) impacted acceleration. Keep the basic statement of N-2 in mind as you script your write up (due Monday), but here are some general ideas for material for your conclusion...
- What does Newton-2 say, conceptually and mathematically, about the relationship between net force, inertia and acceleration? Does your data support this concept? Why or why not?
- What was the net force in this experiment? How would friction impact your results.
- Sources of error? What issues or problems might have contributed to any aberrant data points for your group?
Physics B spent time discussing friction during today's class. We looked at the origin of frictional forces (surface imperfections and adherent electrostatic bonds) and explained why static friction maximum (Fs,max) was larger than kinetic friction (Fk) for any pair of surfaces. The coefficient of friction was introduced and some examples were discussed to better clarify what the coefficient of friction meant for frictional resistance. Tomorrow, we'll go over the homework problems, then get more practice with friction, weight, normal force and net force in preparation for Tuesday's exam.
Introductory Physics had only a few minutes of class time today, due to Peer Mentor stuff, so all we had time for was a quick review of the free fall and kinematics homework. Tomorrow, we'll dig deeper into the impact of free fall on motion by getting a peek at the mechanics of projectile motion.
Honors Physics reviewed the concept of mechanical energy and how it is related to work before jumping into conservation of energy. Total energy is always conserved in systems, but mechanical energy is not. Friction always converts some useful energy into heat, which is non-mechanical and not easily accessible for work, thereby reducing the overall useful mechanical energy in the system. Tomorrow's two lab investigations will have folks looking at conservation of mechanical energy in situations where all of our mechanical energy types (to date) play a role.
10/24/12
You Should Just Fess Up
No one has come forward to claim responsibility for my illness and that's just chicken-baby behavior, if you ask me. So, I get to suffer without retribution against the perpetrator, which would make me feel much better...
Physics A reviewed the concepts of weight and the normal force and got extra practice calculating the normal force for a variety of situations. We'll get back to specific forces on Friday, but tomorrow is set aside for a lab that lets folks examine the tenets of Newton's 2nd law of motion. Physics B conducted that lab today and found that, barring the normal noise in the data, there was a direct relationship between the applied force and the cart's acceleration and an inverse relationship between the cart's inertia and the acceleration (when the applied force was held constant). We'll address any problems or questions for the lab tomorrow, before turning attention to friction.
Introductory Physics reviewed their work with weight and free-fall before getting some focused practice on the kinematics of free free fall. We'll go over those problems tomorrow in class, before adding a layer of complexity to our discussions by looking at orbital or projectile motion.
Honors Physics got a quick review of mechanical energy and were allowed class time to work on problems/questions dealing with kinetic energy, gravitational potential energy, elastic potential energy and the work-energy relationships. Tomorrow, we'll take a look at conservation of energy - a powerful tool for problem solving when the acceleration of an an object cannot be assumed to be constant.
Physics A reviewed the concepts of weight and the normal force and got extra practice calculating the normal force for a variety of situations. We'll get back to specific forces on Friday, but tomorrow is set aside for a lab that lets folks examine the tenets of Newton's 2nd law of motion. Physics B conducted that lab today and found that, barring the normal noise in the data, there was a direct relationship between the applied force and the cart's acceleration and an inverse relationship between the cart's inertia and the acceleration (when the applied force was held constant). We'll address any problems or questions for the lab tomorrow, before turning attention to friction.
Introductory Physics reviewed their work with weight and free-fall before getting some focused practice on the kinematics of free free fall. We'll go over those problems tomorrow in class, before adding a layer of complexity to our discussions by looking at orbital or projectile motion.
Honors Physics got a quick review of mechanical energy and were allowed class time to work on problems/questions dealing with kinetic energy, gravitational potential energy, elastic potential energy and the work-energy relationships. Tomorrow, we'll take a look at conservation of energy - a powerful tool for problem solving when the acceleration of an an object cannot be assumed to be constant.
10/23/12
Just Who Gave Me This Cold?
Someone is going to get the stink-eye from me if I find out who transmitted their plague germs into my personal bubble. Hopefully, I shall not be brung low by this pestilence, but we shall have to see. I am made of stern stuff, after all...
Physics A and B Blocks have been marching through Newton's laws of motion and a few specific forces. Remember that Newton's laws of motion state what objects do when exposed to a zero or non-zero net force and also point a finger at the culprit(s) providing that force. Two of those culprits could be weight and the normal force. Weight is the action of gravity on an object's mass and the normal force is the response of a surface to a press onto it. That response is always perpendicular to the plane of the surface and may or may not line up with the object's weight (which is always straight down). We looked at how to calculate the normal force acting on an object and we'll check over that work tomorrow before diving into friction. Exam coming up next Tuesday and we have a lab to conduct on Newton's 2nd law in the interim, so start gathering questions and making study preparations so you can do your best on the test.
Honors Physics has been discussing the concepts of work and energy. We disentangled the scientific definition of work from how the term is used in daily life and identified examples where objects were having work done on them by a force and when a force was not doing work on the object. Wnet was linked to an object's motion and change/lack of change of motion and further linked, today with the change in energy an object experiences. We defined kinetic, gravitational potential and elastic potential energy and discussed how a change in each of them related to the work that was done on or by an object. We'll look at this some more tomorrow before moving more deeply into energy territory.
Introductory Physics has been laboring with gravity. We looked at Newton's law of universal gravitation yesterday from a conceptual and mathematical standpoint and, today, added in the concepts of free fall, weight and acceleration due to gravity. Remember that free fall only applies when there isn't another force acting on the object's motion besides gravity, such as air resistance, so it isn't applicable to all circumstances. However, many objects moving through the air do approximate free fall and it can be a good predictor for features of the object's motion, such as how high the object rises when thrown upwards or fast it will hit the ground when it is dropped. We'll practice with this idea tomorrow and begin to look at a slightly more complicated model of motion - projectile motion.
Physics A and B Blocks have been marching through Newton's laws of motion and a few specific forces. Remember that Newton's laws of motion state what objects do when exposed to a zero or non-zero net force and also point a finger at the culprit(s) providing that force. Two of those culprits could be weight and the normal force. Weight is the action of gravity on an object's mass and the normal force is the response of a surface to a press onto it. That response is always perpendicular to the plane of the surface and may or may not line up with the object's weight (which is always straight down). We looked at how to calculate the normal force acting on an object and we'll check over that work tomorrow before diving into friction. Exam coming up next Tuesday and we have a lab to conduct on Newton's 2nd law in the interim, so start gathering questions and making study preparations so you can do your best on the test.
Honors Physics has been discussing the concepts of work and energy. We disentangled the scientific definition of work from how the term is used in daily life and identified examples where objects were having work done on them by a force and when a force was not doing work on the object. Wnet was linked to an object's motion and change/lack of change of motion and further linked, today with the change in energy an object experiences. We defined kinetic, gravitational potential and elastic potential energy and discussed how a change in each of them related to the work that was done on or by an object. We'll look at this some more tomorrow before moving more deeply into energy territory.
Introductory Physics has been laboring with gravity. We looked at Newton's law of universal gravitation yesterday from a conceptual and mathematical standpoint and, today, added in the concepts of free fall, weight and acceleration due to gravity. Remember that free fall only applies when there isn't another force acting on the object's motion besides gravity, such as air resistance, so it isn't applicable to all circumstances. However, many objects moving through the air do approximate free fall and it can be a good predictor for features of the object's motion, such as how high the object rises when thrown upwards or fast it will hit the ground when it is dropped. We'll practice with this idea tomorrow and begin to look at a slightly more complicated model of motion - projectile motion.
10/19/12
Forceful Friday
Physics A reviewed their work on the basic properties of forces and free-body diagrams and then turned attention to Newton's 1st law of motion. N-1 states that objects continue with whatever motion they are currently experiencing unless a net external force acts on them. We linked the idea of inertia to this law and discussed how mass is the direct measure of an object's inertia. We also took time to define and explain the concept of equilibrium and how equilibrant forces are calculated On Monday, we carry on with Newton's 2nd law of motion, which will let us quantify the value of acceleration caused by a net force.
Which is what Physics B did today. We discussed, both conceptually and quantitatively, Newton's 2nd law of motion and spent time working practice problems to calculate the net force acting on an object and, subsequently, the object's acceleration. We'll practice this a little more on Monday, when we add Newton-3 to our list, but have to return to Newton-2 to put some numbers to our situations.
Introductory Physics conducted a lab investigation centering on Newton's 2nd law of motion. Newton-2 states that there is a direct relationship between an object's acceleration and the net force it experiences and an inverse relationship between acceleration and the object's inertia, measured by its mass. We tested the acceleration of a cart, where the net force remained steady, but the cart's inertia changed and also the acceleration of a constant-mass cart when the net force was allowed to vary. We'll discuss this lab on Monday, but remember that the lab write up is not due until Tuesday.
Honors Physics basked in the glow of their Chapter 4 exams and will pick up with Chapter 5 - Work and Energy - on Monday.
Have a good weekend!
Which is what Physics B did today. We discussed, both conceptually and quantitatively, Newton's 2nd law of motion and spent time working practice problems to calculate the net force acting on an object and, subsequently, the object's acceleration. We'll practice this a little more on Monday, when we add Newton-3 to our list, but have to return to Newton-2 to put some numbers to our situations.
Introductory Physics conducted a lab investigation centering on Newton's 2nd law of motion. Newton-2 states that there is a direct relationship between an object's acceleration and the net force it experiences and an inverse relationship between acceleration and the object's inertia, measured by its mass. We tested the acceleration of a cart, where the net force remained steady, but the cart's inertia changed and also the acceleration of a constant-mass cart when the net force was allowed to vary. We'll discuss this lab on Monday, but remember that the lab write up is not due until Tuesday.
Honors Physics basked in the glow of their Chapter 4 exams and will pick up with Chapter 5 - Work and Energy - on Monday.
Have a good weekend!
10/18/12
Continuing on With Forces
Physics A went over their Chapter 3 exams, then turned attention to forces. We discussed the nature of forces, the difference between contact and field forces and the use of free-body diagrams to document the forces acting on an object. We'll use those free-body diagrams tomorrow to help us with our calculations of net force acting on an object. Physics B did this yesterday and was supposed to move on to Newton's 2nd and 3rd laws of motion, but we took extra time to go over the test and homework, so that will be the focus of tomorrow's work.
Honors Physics reviewed their lab investigation and also the last batch of homework before addressing any last-minute issues for tomorrow's exam. If you need more discussion about the latter problem types, don't forget to check out the videos that were posted yesterday. Monday - Work and Energy!
Introductory Physics reviewed their Chapter 10 exams and then turned attention to more concepts associated with forces. Newton's 1st and 2nd laws of motion. The 1st law of motion describes how the motion of an object is governed by its inertia until the object is acted upon by a net external force. Even if forces act on the object, if the Fnet = 0, the object's remains unchanged. We then took a look at the 2nd law to discover a way to assess the magnitude of the object's change of motion. The acceleration an object experiences is directly proportional to the Fnet and inversely proportional to the object's inertia, measured by its mass. The equation associated with Newton-2 (Fnet = ma is the quantitative way of assessing the size of the object's acceleration or or applied external force. Tomorrow, we'll check over the homework problems, add a few more for practice, then turn our attention to a specialized acceleration - acceleration due to gravity - and how it is involved with a specialized force known as weight.
Honors Physics reviewed their lab investigation and also the last batch of homework before addressing any last-minute issues for tomorrow's exam. If you need more discussion about the latter problem types, don't forget to check out the videos that were posted yesterday. Monday - Work and Energy!
Introductory Physics reviewed their Chapter 10 exams and then turned attention to more concepts associated with forces. Newton's 1st and 2nd laws of motion. The 1st law of motion describes how the motion of an object is governed by its inertia until the object is acted upon by a net external force. Even if forces act on the object, if the Fnet = 0, the object's remains unchanged. We then took a look at the 2nd law to discover a way to assess the magnitude of the object's change of motion. The acceleration an object experiences is directly proportional to the Fnet and inversely proportional to the object's inertia, measured by its mass. The equation associated with Newton-2 (Fnet = ma is the quantitative way of assessing the size of the object's acceleration or or applied external force. Tomorrow, we'll check over the homework problems, add a few more for practice, then turn our attention to a specialized acceleration - acceleration due to gravity - and how it is involved with a specialized force known as weight.
10/17/12
The Force is Strong
Physics A completed their Static and Kinetic Friction lab today and the write up is due on Friday. Hopefully, you took a look at the hints I put on the board for your Conclusion section and are going to take a sneak peek at the friction section of this chapter to help make meaning of your results. Tomorrow, we'll start on a discussion about the nature of forces.
Physics B used their work with the nature of forces to make an inroad into Newton's laws of motion. We tackled Newton's 1st in class today and got some practice problem solving using N-1. Make sure you fully understand the implications of Newton's 1st and that you can use the free-body diagrams you practiced yesterday to calculate the net force acting on an object. Tomorrow, we'll see how to calculate the acceleration that force produces in conjunction with another topic we discussed today - inertia. Keep in mind that inertia is measured by an object's mass and nothing else. That will help when we work with Newton's 2nd law tomorrow.
Introductory Physics enjoyed their graded learning experience for Chapter 10 this afternoon. Tomorrow, we'll go over that exam and start to head deeper into the great Force Forest.
Honors Physics conducted a lab that had folks investigating both static and kinetic friction. We measured these values using both a force sensor and a motion detector, and used the information to calculate coefficients of friction. We'll discuss the lab tomorrow as part of our Chapter 4 review, but the write up is not due until Monday. Overall, tomorrow is set aside for exam preparation, so come with questions. As promised, I put together a few videos for working with that pesky net force-acceleration situation:
Easiest
Physics B used their work with the nature of forces to make an inroad into Newton's laws of motion. We tackled Newton's 1st in class today and got some practice problem solving using N-1. Make sure you fully understand the implications of Newton's 1st and that you can use the free-body diagrams you practiced yesterday to calculate the net force acting on an object. Tomorrow, we'll see how to calculate the acceleration that force produces in conjunction with another topic we discussed today - inertia. Keep in mind that inertia is measured by an object's mass and nothing else. That will help when we work with Newton's 2nd law tomorrow.
Introductory Physics enjoyed their graded learning experience for Chapter 10 this afternoon. Tomorrow, we'll go over that exam and start to head deeper into the great Force Forest.
Honors Physics conducted a lab that had folks investigating both static and kinetic friction. We measured these values using both a force sensor and a motion detector, and used the information to calculate coefficients of friction. We'll discuss the lab tomorrow as part of our Chapter 4 review, but the write up is not due until Monday. Overall, tomorrow is set aside for exam preparation, so come with questions. As promised, I put together a few videos for working with that pesky net force-acceleration situation:
Easiest
In the Middle
Hardest
10/16/12
Fiddling with Forces
Physics B discussed yesterday's friction lab before jumping into our new unit on forces. Friction is a specific force, but it does what all forces do - act to accelerate objects. We discussed the idea of net force (Fnet) and what it meant when Fnet = 0 N and ≠ 0 N. You should be able to calculate the net force acting on any object and be prepared to draw a free-body diagram to document the forces that were included in the net force calculation. Remember that forces can be contact forces, like a physical push or pull, or field forces, like gravitational or magnetic forces, but they do the same job and contribute to net force calculations. Tomorrow, we'll start to specifically line forces to motion and changes in motion as we dive into Newton's laws of motion.
Physics A started a lab investigation on static and kinetic friction. Static friction acts on objects at rest on surfaces and kinetic friction acts on objects in motion across or through surfaces. Both frictional forces arise from irregularities on the surfaces of the materials in contact, but static friction is boosted by the formation of adhesive, electrostatic bonds between the surfaces. Because of this, for the same objects in contact, the peak static friction (Fs,max) will always be greater than the kinetic friction (Fk). The data you are collecting is showing this relationship nicely and slotting in the additional concept of coefficient of friction. We'll talk about that tomorrow as more groups get to that calculation and discuss what it means specifically for our surfaces in the experiment.
Introductory Physics reviewed their MCAS practice for motion and certain force ideas. Folks seemed to do a nice job with that, but the open responses could have used more clarity, organization, detail and vocabulary for some questions. We'll practice this throughout the year, but start looking at your short answer questions and homework questions with an eye towards how this question would score if someone was grading it for your MCAS. Tomorrow is test day and on Thursday, we'll get deeper into the ideas of forces.
Honors Physics had more practice with working with forces and force diagrams. A good sketch, with all forces identified and labeled is a great help in solving these problems. Sometimes it is easiest to work backwards with these situations. Writing down what you are asked to determine (acceleration, net force, coefficient of friction, etc.) can start you thinking about what you directly need to solve for that variable (and there may be more than one possible pathway that you'll pare down to one as you evaluate the information), then what do you need to solve for the things to solve for that, etc. Tomorrow's lab will give you a better idea about the conceptual nature of friction and the coefficient of friction and we'll take Thursday to review the chapter ideas and tonight's homework. Test of Friday, so be prepared. I'll get a couple of videos up tomorrow for working with forces that might help you with the problems due on Thursday.
Physics A started a lab investigation on static and kinetic friction. Static friction acts on objects at rest on surfaces and kinetic friction acts on objects in motion across or through surfaces. Both frictional forces arise from irregularities on the surfaces of the materials in contact, but static friction is boosted by the formation of adhesive, electrostatic bonds between the surfaces. Because of this, for the same objects in contact, the peak static friction (Fs,max) will always be greater than the kinetic friction (Fk). The data you are collecting is showing this relationship nicely and slotting in the additional concept of coefficient of friction. We'll talk about that tomorrow as more groups get to that calculation and discuss what it means specifically for our surfaces in the experiment.
Introductory Physics reviewed their MCAS practice for motion and certain force ideas. Folks seemed to do a nice job with that, but the open responses could have used more clarity, organization, detail and vocabulary for some questions. We'll practice this throughout the year, but start looking at your short answer questions and homework questions with an eye towards how this question would score if someone was grading it for your MCAS. Tomorrow is test day and on Thursday, we'll get deeper into the ideas of forces.
Honors Physics had more practice with working with forces and force diagrams. A good sketch, with all forces identified and labeled is a great help in solving these problems. Sometimes it is easiest to work backwards with these situations. Writing down what you are asked to determine (acceleration, net force, coefficient of friction, etc.) can start you thinking about what you directly need to solve for that variable (and there may be more than one possible pathway that you'll pare down to one as you evaluate the information), then what do you need to solve for the things to solve for that, etc. Tomorrow's lab will give you a better idea about the conceptual nature of friction and the coefficient of friction and we'll take Thursday to review the chapter ideas and tonight's homework. Test of Friday, so be prepared. I'll get a couple of videos up tomorrow for working with forces that might help you with the problems due on Thursday.
10/15/12
Friction
Physics A and B enjoyed their Chapter 3 exam, but B Block got to take advantage of the scheduled long block and use the second half of the period to conduct a lab investigation on friction. Students investigated kinetic friction and how it was affected by the surface texture of the materials in question. Attention then turned to the coefficient of friction, which gives some quantitative measure as to how surface textures influence friction. We'll go over the lab tomorrow before heading (with A Block) into forces and Newton's laws of motion.
Introductory Physics reviewed for their Chapter 10 test, which is scheduled for Wednesday. We went over the weekend's homework before walking page through page through the chapter, highlighting information and skills necessary for Wednesday and pointing out things we covered in class that are NOT in the chapter. Folks were sent home with two packets of review material made up of questions from old MCAS exams. We'll go over them in class tomorrow and address any last-minute issues for Wednesdays assessment.
Honors Physics reviewed the concept of the normal force (FN) and added in how to calculate the normal force when objects are on inclines and/or are being acted on by an applied force. Remember that the normal force generated by a surface will be equal and opposite to the magnitude of the force pressing down on it. If you are lifting up or pressing down on an object, that force will subtract or add to the object's weight (or component of the object's weight) and influence the size of the resulting normal force. We then linked normal force to friction. Static and kinetic friction were contrasted and will be the subject of Wednesday's lab. We looked at the factors that promoted frictional resistance and how the coefficient of friction and normal force were used to calculate the size of the frictional force an object experiences on or moving across a surface. We'll practice more with this tomorrow, along with how friction and the normal force factor into calculating the net force acting on a object and the resulting acceleration.
Introductory Physics reviewed for their Chapter 10 test, which is scheduled for Wednesday. We went over the weekend's homework before walking page through page through the chapter, highlighting information and skills necessary for Wednesday and pointing out things we covered in class that are NOT in the chapter. Folks were sent home with two packets of review material made up of questions from old MCAS exams. We'll go over them in class tomorrow and address any last-minute issues for Wednesdays assessment.
Honors Physics reviewed the concept of the normal force (FN) and added in how to calculate the normal force when objects are on inclines and/or are being acted on by an applied force. Remember that the normal force generated by a surface will be equal and opposite to the magnitude of the force pressing down on it. If you are lifting up or pressing down on an object, that force will subtract or add to the object's weight (or component of the object's weight) and influence the size of the resulting normal force. We then linked normal force to friction. Static and kinetic friction were contrasted and will be the subject of Wednesday's lab. We looked at the factors that promoted frictional resistance and how the coefficient of friction and normal force were used to calculate the size of the frictional force an object experiences on or moving across a surface. We'll practice more with this tomorrow, along with how friction and the normal force factor into calculating the net force acting on a object and the resulting acceleration.
10/14/12
Friday's Fun and Test Review
Physics A and B spent Friday reviewing for Monday's exam on 2-dimensional motion and vectors. Here are two videos to help you prepare for that test, especially if you were absent on Friday. The first is a walk through the chapter and the second takes on three problem types that will show up on the exam: non-perpendicular vectors, horizontally-launched projectiles and projectiles launched at an angle...
Honors Physics reviewed their Chapter 3 exams and Newton's laws of motion before continuing on with specific forces. We covered weight on Thursday and connected that idea with the new topic of the normal force (FN). As long as an object is on a horizontal surface and no one is pushing or pulling on it at an angle, the weight of the object is equal and opposite to the normal force provided by the surface. If the object is on an incline, only a component of the object's weight (mgcosΘ)is equal and opposite to the normal force. We'll look at how applied forces impact the normal force on Monday, as well as start a discussion about friction.
Introductory Physics worked with friction on Friday. We defined friction, contrasted static and kinetic friction and looked at examples of sliding, rolling and fluid friction. Make sure you are clear on the definition of all those terms and the reasons why some forms of friction are greater/lesser in magnitude than other forms. We'll look at this again tomorrow, review the chapter on Tuesday and have our Chapter 10 exam on Wednesday.
10/11/12
Forces
Introductory Physics took time to review yesterday's lab that focused on the topic of friction. We'll add a number of details to our discussion about friction during tomorrow's class, but the information we went over today should be enough to help you interpret your data and write up your lab. We postponed the due date for that from tomorrow to Monday, so you should have plenty of time to craft a good conclusion section, including any research time you might choose to use to enhance that section of your lab write up.
Honors Physics reviewed their work on Newton's 1st and 2nd laws of motion before tackling the last sibling in that series of triplets - Newton's 3rd law of motion. This one sometimes gives people a little difficulty, so be clear that you understand that forces occur in pairs. Each member of the pair is equal in magnitude, but opposite in direction to the other. This does not mean, in any way, that the accelerations of the interacting objects will be equal and opposite. The accelerations will be based on the object's inertia, measured by their masses. So, if a mosquito hits a car's windshield, the mosquito and the windshield both experience the same magnitude of force. However, the mosquito will have a much larger acceleration due to the smaller inertia. Newton's 3rd works with contact forces as well as with field forces such as gravity. In our discussion of weight (Fg), we used the pull of gravity on objects to show how both objects are influenced by the shared size of a pull, but how their resulting behaviors differ. Tomorrow, we'll start to look at the remaining of what your book calls "Everyday Forces," - the normal force (FN) and friction (Fk,s).
Physics A and B reviewed their work with projectiles launched at an angle and took more practice with that topic during the class period. We'll have a general review for this chapter in class tomorrow to prepare for Monday's exam, so come with questions!
Honors Physics reviewed their work on Newton's 1st and 2nd laws of motion before tackling the last sibling in that series of triplets - Newton's 3rd law of motion. This one sometimes gives people a little difficulty, so be clear that you understand that forces occur in pairs. Each member of the pair is equal in magnitude, but opposite in direction to the other. This does not mean, in any way, that the accelerations of the interacting objects will be equal and opposite. The accelerations will be based on the object's inertia, measured by their masses. So, if a mosquito hits a car's windshield, the mosquito and the windshield both experience the same magnitude of force. However, the mosquito will have a much larger acceleration due to the smaller inertia. Newton's 3rd works with contact forces as well as with field forces such as gravity. In our discussion of weight (Fg), we used the pull of gravity on objects to show how both objects are influenced by the shared size of a pull, but how their resulting behaviors differ. Tomorrow, we'll start to look at the remaining of what your book calls "Everyday Forces," - the normal force (FN) and friction (Fk,s).
Physics A and B reviewed their work with projectiles launched at an angle and took more practice with that topic during the class period. We'll have a general review for this chapter in class tomorrow to prepare for Monday's exam, so come with questions!
10/10/12
Back in the Saddle
After the extended weekend (with a teacher professional development day tossed in for good measure), folks were raring to pick up where they left off on Friday...
Physics A and B reviewed their work with horizontally-launched projectiles before launching into projectiles launched at an angle. We'll concentrate on projectiles for which the launch and landing heights are equal to facilitate problem solving. Remember to break your initial launch velocity into x- and y-components and use these components in your kinematics formulas. Keep in mind that the velocity in the x-direction is constant, the acceleration in the y-direction is -9.81 m/s2, the velocity in the y-direction at the maximum height is 0 m/s and that the trajectory of the projectile will be a symmetrical parabola. You should be able to solve for horizontal range (Δx), maximum height (Δymax) and total time in the air. We worked a sample problem in class today and there are a couple of videos posted a few days ago that you can watch to see other examples. We'll go over the homework tomorrow and if more practice is needed, we have time to do just that. Review time on Friday and exam on Monday - be prepared!
Introductory Physics engaged in a lab investigation that had people exploring the concept of friction. The impact of surface texture, surface area and mass on friction was evaluated and data was collected to let folks calculate the coefficient of kinetic friction (μk). That concept isn't discussed in your books, so we'll take time in class tomorrow to provide some background information on this and other concepts associated with the lab. The write up isn't due until Friday, so you'll have time to incorporate these ideas into your work.
Honors Physics built on their work with force and Fnet to discuss Newton's 1st and 2nd laws of motion. Add the new vocabulary of inertia, equilibrium and equilibriant to your terminology suitcase. Also, make sure you are very clear, conceptually, on what those first two laws of motion have to say in terms of the impact of force on motion. Be able to, also, solve problems using Newton's 2nd law of motion. You may have to do some work to calculate the net force first, but it is just familiar old vector work, so don't be nervous about jumping right in. We'll go over the homework items tomorrow before taking a look at Newton's 3rdlaw of motion.
Physics A and B reviewed their work with horizontally-launched projectiles before launching into projectiles launched at an angle. We'll concentrate on projectiles for which the launch and landing heights are equal to facilitate problem solving. Remember to break your initial launch velocity into x- and y-components and use these components in your kinematics formulas. Keep in mind that the velocity in the x-direction is constant, the acceleration in the y-direction is -9.81 m/s2, the velocity in the y-direction at the maximum height is 0 m/s and that the trajectory of the projectile will be a symmetrical parabola. You should be able to solve for horizontal range (Δx), maximum height (Δymax) and total time in the air. We worked a sample problem in class today and there are a couple of videos posted a few days ago that you can watch to see other examples. We'll go over the homework tomorrow and if more practice is needed, we have time to do just that. Review time on Friday and exam on Monday - be prepared!
Introductory Physics engaged in a lab investigation that had people exploring the concept of friction. The impact of surface texture, surface area and mass on friction was evaluated and data was collected to let folks calculate the coefficient of kinetic friction (μk). That concept isn't discussed in your books, so we'll take time in class tomorrow to provide some background information on this and other concepts associated with the lab. The write up isn't due until Friday, so you'll have time to incorporate these ideas into your work.
Honors Physics built on their work with force and Fnet to discuss Newton's 1st and 2nd laws of motion. Add the new vocabulary of inertia, equilibrium and equilibriant to your terminology suitcase. Also, make sure you are very clear, conceptually, on what those first two laws of motion have to say in terms of the impact of force on motion. Be able to, also, solve problems using Newton's 2nd law of motion. You may have to do some work to calculate the net force first, but it is just familiar old vector work, so don't be nervous about jumping right in. We'll go over the homework items tomorrow before taking a look at Newton's 3rdlaw of motion.
10/6/12
Forces and Motion
Honors Physics and Introductory Physics jumped into the arena of forces yesterday, with a look at the nature of forces, the ability to combine force vectors to find net force and the use of free-body diagrams to analyze the forces acting on an object. Honors Physics took a harder look at calculating net force and those folks should be able to combine any and any number of force vectors to determine Fnet. We'll look at how to use that to assess an object's acceleration next week. For Introductory Physics, be able to calculate Fnet for forces that are in the same direction or opposite directions and be sure you are clear about the distinction between balanced and unbalanced forces. For both groups, don't lose sight of the meaning of Fnet = 0 N. It means no net force, balanced forces, no acceleration and object moves with constant velocity. Also for both groups, remember that only forces that act directly on an object are included in free-body diagrams, not forces that the object applies to other objects. Next week, Introductory Physics takes a look at friction and Honors Physics steps into Newton's laws of motion.
Physics A and B both worked on evaluating horizontally-launched projectiles. For horizontally-launched projectiles, remember that some information important for problems solving won't be directly stated in the problem. The fact that the initial velocity in the y-direction is 0 m/s and the velocity in the x-direction is constant (and the stated launch velocity), won't be spelled out for you. Also, remember that accelration in the y-direction is -9.81 m/s2 and is 0 m/s2 in the x-direction. The time you calculate for the object to hit the landing point is the same time as for the ball to cover the horizontal range. You need all that information in your pocket, along with any explicit information in order to work these problems. We'll go over the homework items on Wednesday when we return from the extra-long weekend and then add a layer of complexity by tackling projectiles launched at an angle.
Physics A and B both worked on evaluating horizontally-launched projectiles. For horizontally-launched projectiles, remember that some information important for problems solving won't be directly stated in the problem. The fact that the initial velocity in the y-direction is 0 m/s and the velocity in the x-direction is constant (and the stated launch velocity), won't be spelled out for you. Also, remember that accelration in the y-direction is -9.81 m/s2 and is 0 m/s2 in the x-direction. The time you calculate for the object to hit the landing point is the same time as for the ball to cover the horizontal range. You need all that information in your pocket, along with any explicit information in order to work these problems. We'll go over the homework items on Wednesday when we return from the extra-long weekend and then add a layer of complexity by tackling projectiles launched at an angle.
10/4/12
Rain
A whole summer of nothing and now it won't stop raining. And I can't stay home, curled up with popcorn and a movie, to enjoy it...
Physics A and B reviewed their work with non-perpendicular vectors and it was decided in both classes that a little more practice was necessary before moving on. So, we worked through more examples and we'll wait to take on horizontal projectiles until tomorrow.
Introductory Physics also had an additional practice day. The graphing portion of yesterday's quiz indicated that some folks still needed a little work in that area, so we worked on a problem that involved graphing and a bit of the ol' kinematics formulas. We'll check over that tomorrow to make sure everyone's feeling good about graphing before taking on forces.
Honors Physics took their postponed Chapter 3 exam. We wound up using most of the long block, but that's not a problem in the grand scheme of the year's schedule. Tomorrow, we dive into forces and Newton's laws of motion.
Physics A and B reviewed their work with non-perpendicular vectors and it was decided in both classes that a little more practice was necessary before moving on. So, we worked through more examples and we'll wait to take on horizontal projectiles until tomorrow.
Introductory Physics also had an additional practice day. The graphing portion of yesterday's quiz indicated that some folks still needed a little work in that area, so we worked on a problem that involved graphing and a bit of the ol' kinematics formulas. We'll check over that tomorrow to make sure everyone's feeling good about graphing before taking on forces.
Honors Physics took their postponed Chapter 3 exam. We wound up using most of the long block, but that's not a problem in the grand scheme of the year's schedule. Tomorrow, we dive into forces and Newton's laws of motion.
10/3/12
A Day of Variety
Physics B reviewed their projectile motion lab and their work on resolving vectors before plunging headlong into the topic of non-perpendicular vectors. Make sure to carefully follow the steps we listed in class and pay attention to the sign of each vector. The video posted yesterday will give you a review of this process if you need a little reminding. Tomorrow, we'll go over these problems and then take a deeper look into the properties of horizontally-launched projectiles.
Physics A investigated the motion of a horizontally-launched projectile during today's long block. With a few measurements, folks were able to calculate a target distance and land a ball bearing right in a plastic cup. Then, the task was to calculate and set a launch velocity to hit a given target distance. We'll go over the lab tomorrow before we review our work on non-perpendicular vectors. Then, we'll use the lab to highlight the general discussion about properties of horizontally-launched projectiles. If you didn't get a chance to copy the Summary of Results and Conclusion ideas from the board, check out yesterday's post...
Introductory Physics took their graphing motion and kinematics quiz. Overall, the kinematics portion wasn't bad, but the graphing still needs work. That's fine...we have time...
Honors Physics had their test postponed until tomorrow. With 5 students being dismissed 25 minutes early and another few being absent, giving the exam today wasn't perhaps the best use of time. So, students had more review time and we'll work on the exam tomorrow in class. Time permitting, we'll conduct some investigation associated with forces, but we'll have to see how the period plays out...
Physics A investigated the motion of a horizontally-launched projectile during today's long block. With a few measurements, folks were able to calculate a target distance and land a ball bearing right in a plastic cup. Then, the task was to calculate and set a launch velocity to hit a given target distance. We'll go over the lab tomorrow before we review our work on non-perpendicular vectors. Then, we'll use the lab to highlight the general discussion about properties of horizontally-launched projectiles. If you didn't get a chance to copy the Summary of Results and Conclusion ideas from the board, check out yesterday's post...
Introductory Physics took their graphing motion and kinematics quiz. Overall, the kinematics portion wasn't bad, but the graphing still needs work. That's fine...we have time...
Honors Physics had their test postponed until tomorrow. With 5 students being dismissed 25 minutes early and another few being absent, giving the exam today wasn't perhaps the best use of time. So, students had more review time and we'll work on the exam tomorrow in class. Time permitting, we'll conduct some investigation associated with forces, but we'll have to see how the period plays out...
10/2/12
Projectiles
Physics A took time to discuss and practice techniques for working with non-perpendicular vectors. When vectors don't make a nice right triangle on their own, we must take a more complex approach to combining them. Remember the steps:
Honors Physics reviewed their work on projectiles launched at an angle and also had a general review for tomorrow's exam. On Thursday, we move on to forces and the Newton's Laws of Motion.
- Sketch the situation, double-checking the direction of each vector.
- Resolve each vector into x- and y-components, paying close attention to signs.
- Sum all of the x-components and y-components for the vectors.
- Make a right triangle with the Σx and Σy values.
- Solve for the resultant, remembering both magnitude and direction.
I'll try and post a video for working with non-perpendicular vectors later today. We'll go over your homework problems on Thursday, so make sure you see me if you need extra help. Tomorrow - a lab on projectile motion. Physics B worked on the projectile motion lab in class today, calculating the landing point of a horizontally-launched projectile and testing how accurate was their prediction/calculation. Given a measured launch velocity and other bits of information, all groups hit their targets on the first try. Some groups got to engage in the Extension, where a target distance was set and the launch velocity had to be calculated (and then established). We'll go over projectile motion in more detail towards the end of the week, but remember our discussion at the start of class and use the following guidelines for helping you with your lab write up:
Summary of Results:
Main experiment - Given a table height of _______ and a launch velocity of _______, we predicted a landing distance of _______ and hit/failed to hit the target.
Extension - Given a target distance of _______ and a table height of ________, we predicted a launch speed of _______ and hit/failed to hit the target. Conclusion Ideas:
Conclusion Ideas:
- What is projectile motion?
- Why can we factor out air resistance for the ball bearing's motion?
- How did you make your predictions?
- What assumptions did you make?
- What information, measured or not, did you use?
- Why was vx constant?
- Why did the trajectory of the motion look like half a parabola?
Honors Physics reviewed their work on projectiles launched at an angle and also had a general review for tomorrow's exam. On Thursday, we move on to forces and the Newton's Laws of Motion.
10/1/12
The Math of Motion
Introductory Physics had the whole period set aside to practice working with the kinematics formulas on their MCAS formula sheet. As we go through the year, you'll see why organizing your work is very important for success. List your information (variable, value, unit, direction) and don't hesitate to actually write down the variable for which you'll be solving. Read the problem again for any information given in words (at rest = vi = 0 m/s, for example) and add that to your list. Look at your formula sheet and see if there is any equation that directly lets you use your list of information to solve for your desired variable. Sometimes you get lucky, other times you don't. If there's not one equation, look for an equation that will use your current information to add more to the information list. That may crack open a formula that let's you get to the desired end point. At this level, it is not about being given numbers and just plugging them into an equation; at this level, you are expected to be able to plan an attack with what you're given to conquer the problem, regardless of how many steps you need to get to that victory. We'll go over the problems tomorrow and take more practice if it is needed. If not - on with more motion!
Physics A and B moved into the topic of vector resolution today. On Friday, we showed how two perpendicular vectors could be combined into a resultant that had both magnitude and direction; today we turned around and went backwards. Vector resolution takes a single vector with magnitude and direction and breaks it apart into two perpendicular components. We introduced the sine and cosine functions to solve for horizontal and vertical components of vectors and the practice you did with this technique, along with Friday's vector combination practice, will help you solve problems throughout the year. Tomorrow, we combine the two techniques to tackle the slightly more complex situation of non-perpendicular vectors.
Honors Physics had a great time since I wasn't in class, though why I found the remnants of balloons and llama fur in my room when I returned shall happily remain a mystery. Folks got more practice with projectiles launched at an angle and these problems were a bit more complex than the ones we worked last week. If you get stuck, check the online solutions or go back and watch yesterday's videos. We'll go over these problems tomorrow as part of our general review for Wednesday's exam.
Physics A and B moved into the topic of vector resolution today. On Friday, we showed how two perpendicular vectors could be combined into a resultant that had both magnitude and direction; today we turned around and went backwards. Vector resolution takes a single vector with magnitude and direction and breaks it apart into two perpendicular components. We introduced the sine and cosine functions to solve for horizontal and vertical components of vectors and the practice you did with this technique, along with Friday's vector combination practice, will help you solve problems throughout the year. Tomorrow, we combine the two techniques to tackle the slightly more complex situation of non-perpendicular vectors.
Honors Physics had a great time since I wasn't in class, though why I found the remnants of balloons and llama fur in my room when I returned shall happily remain a mystery. Folks got more practice with projectiles launched at an angle and these problems were a bit more complex than the ones we worked last week. If you get stuck, check the online solutions or go back and watch yesterday's videos. We'll go over these problems tomorrow as part of our general review for Wednesday's exam.
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