Forceful Friday

Physics A reviewed their work on the basic properties of forces and free-body diagrams and then turned attention to Newton's 1^st 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 2^nd 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 2^nd 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 2^nd 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!

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 2^nd and 3^rd 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 1^st and 2^nd laws of motion. The 1^st 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 F_net = 0, the object's remains unchanged. We then took a look at the 2^nd 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 F_net and inversely proportional to the object's inertia, measured by its mass. The equation associated with Newton-2 (F_net = 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.

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 1^st in class today and got some practice problem solving using N-1. Make sure you fully understand the implications of Newton's 1^st 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 2^nd 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

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 (F_net) and what it meant when F_net = 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 (F_s,max) will always be greater than the kinetic friction (F_k). 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.

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 (F_N) 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.

I Do NOT Want Diaper Duty

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 (F_N). 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.

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 1^st and 2^nd laws of motion before tackling the last sibling in that series of triplets - Newton's 3^rd 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 3^rd works with contact forces as well as with field forces such as gravity. In our discussion of weight (F_g), 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 (F_N) and friction (F_k,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!

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 (Δy_max) 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 (μ_k). 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 F_net to discuss Newton's 1^st and 2^nd 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 2^nd 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 3^rdlaw of motion.

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 F_net. We'll look at how to use that to assess an object's acceleration next week. For Introductory Physics, be able to calculate F_net 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 F_net = 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.

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.

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...

Non-Perpendicular Vectors

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:

1. Sketch the situation, double-checking the direction of each vector.
2. Resolve each vector into x- and y-components, paying close attention to signs.
3. Sum all of the x-components and y-components for the vectors.
4. Make a right triangle with the Σx and Σy values.
5. 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 v_x constant?
• Why did the trajectory of the motion look like half a parabola?

Introductory Physics reviewed their kinematics problems and we worked some extra for additional practice as a class. A 5-question quiz tomorrow will check both your ability to interpret/create graphs of motion and your skills with kinematics. Then, it is on to an introduction to how forces impact motion (covered in more detail in the next chapter).

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.

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 = v_i = 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.