Rotational Motion

Honors Physics continued on today with their study of rotational dynamics with an overview of moment of inertia and rotational equilibrium. Moment of inertia stands in for mass in rotational systems - mass distribution is very important for extended objects and their overall motion. For equilibrium, we had to add on a new condition - an object in complete equilibrium must be subject to both zero net force and zero net torque. So, an object can be in translational equilibrium, rotational equilibrium, both or neither. The problem set you have tonight assumes complete equilibrium and uses that scenario to have you determine the magnitude of forces. The solutions are on Edline and here's another link for you to use.

Physics B and Physics F completed their circular motion labs. No one got a black eye from getting whacked with a rubber stopper, so it was a great success. We'll talk about the lab tomorrow before heading into rotational dynamics.

Physical Science completed their two simple machine experiments. The inclined plane reduces your effort force by providing more distance through which to put the force. The first and second class levers do the same thing. Third class levers make you put in more force than the machine gives out, but that is good if you need to do some delicate work (like with computer circuitry) or if you need an increase of distance, instead. Tomorrow, we'll use the labs to help introduce our unit on work, power and simple machines.

Homework

Honors Physics - Practice 8B #2, 3 and 4
Physics B and F: Complete Centripetal Force and Speed lab write up
Physical Science: Complete Inclined Plane and Levers lab write up

More Monday, No Turkey

Hopefully, everyone had a nice Thanksgiving vacation and got a chance to rest and relax. Now, back to work...

Honors Physics began their chapter on rotational dynamics with a discussion of torque and center of mass. Torque acts as a force analogue in rotational motion - forces with the same magnitude to not produce the same rotation if applied to different locations or at different angles. Net torque, also, is analogous to net force: a nonzero net torque produces rotational acceleration, zero net torque keeps the object in equilibrium. Torques is going to come again soon when we begin to look at Newton's laws from a rotational perspective. Attention then turned to center of mass and its role in rotation. The center of can be thought of as the natural axis of rotation for an object, since it is around this point an object will spin when acting only under the force of gravity. We discussed examples of this and also the role of center of mass/gravity (not the same thing, but close enough for our purposes) plays in stability. Tomorrow - moment of inertia!

Physics B began an investigation on centripetal force, rotational radius and rotational speed. Students maintained a constant radius for a stopper being whirled on a string and determined how the centripetal force affected the rotational speed required to maintain this radius. We'll finish up the lab tomorrow before turning, on Wednesday, towards rotational mechanics.

Physics F launched into a discussion of rotational motion by examining the descriptors of rotational motion and linking them to the concept of centripetal force. Many people use the term centrifugal force in this arena and time was taken to clear up that misconception. We also added in a little on center of gravity. Tomorrow, a lab that looks at centripetal force and angular speed for a system demonstrating rotational motion.

Physical Science took their force and momentum exam and then began the first of two lab investigations into the area of work and simple machines. The inclined plane was the focus of this lab and we'll continue with it and add in levers tomorrow.

Homework

Honors Physics: Practice 8A and the 8.1 Section Review
Physics B and F: None
Physical Science: 12.1 Section Review

Phryday!

Honors Physics spent some time discussing the idea of centripetal force. Remember, that term is really a job description. Different forces perform that role, depending on the the situation. The direction of the force matches the direction of centripetal acceleration - towards the center of the circle/axis of rotation. Time was then given for students to practice solving problems for rotational motion. We'll go over those on Monday before turning attention to gravity. We've looked at acceleration due to gravity and verified the value in lab. Now, how do we calculate how big is the force that produced that acceleration?

Physics B watched a Mythbusters segment that introduced the upcoming unit on circular motion and also reinforced concepts for force, momentum and pressure. We'll start up with circular motion on Monday and Tuesday's lab will allow you to observe the effects of mass and rotational radius on the magnitude of centripetal force. Physics F endured their work and energy exam, so not much to report on that front.

Physical Science concluded their MCAS review for force, laws of motion and momentum. We'll review these topics and upcoming ones as we go along through the year and take last year's full test as a status check before the real test in June.

Homework:

Honors Physics: 7E #1, 2; 7F #1, 3; 7G #1, 3, 5; 7H #1, 4; p. 271 #47
Physics B: Complete Mythbusters discussion questions:

1. List 5 things that move with circular motion. Explain how they are able to move in a circle - why don't they just move in a straight line (Hint: think about force).


2. Do you enjoy rides that move with circular motion. Why or why not?

Physics F: None
Physical Science: None

Child's Play

Ok, so there's a new link on the sidebar and it asks you to donate. If you don't know about Child's Play charity, click on the logo and read what these people do. Powered by the gamer community, the proceeds and items go help sick kids. I donate every year, to the Children's Hospital in Boston, through their Amazon.com Wish List and also choose another hospital, from my home state of Louisiana or out of the country to contribute. Last year, I sent a sweet Xbox 360 pack to two hospitals to let kids stuck in hospital beds forget about their troubles for a little bit while playing whatever little kids play - Viva Pinata or Barbie's Horse Adventures or something. Regardless, its a good deed and something that shows that gamers aren't the crazed maniacs that the press sometimes likes to portray. Last year, they took in over 1.5 million in cash and toys...if you have a few extra bucks and you consider yourself part of the gaming community, consider donating to help some kid who might be spending the holidays in a hospital rather that at home with their folks. Gamers rock the house and its time the world caught on to that fact. Ok, rant and propaganda time over with. See everyone tomorrow...

PTCR2

Round 2 of parent-teacher conferences...students get a half-day and we get a long lunch...everyone gets a little something nice...

Honors Physics went over their momentum exams before reviewing last nights homework for kinematics of angular motion. Attention then turned to exploring the relationship between tangential motion and rotational motion for objects and added a new player to the game - centripetal acceleration. Tomorrow, we'll look at forces that can promote circular motion and see why they all get lumped into a single category - centripetal force.

Physics B took their work and energy exam. Tomorrow, we take up rotational motion and keep that track for the next couple of chapters.

Physics F and Physical Science didn't meet due to the half-day schedule

Homework

None for anyone!

PTCR1

Parent-Teacher Conferences tonight and tomorrow, so make sure to be very polite at home to buffer "the talk" you'll get when your parents come home afterward...

Honors Physics embarked on a study of rotational motion. The nice thing for this first piece is that the topics are familiar - displacement, speed, acceleration, kinematics - they just have a slightly different twist. Once you orient yourself as to how to define angular displacement, the rest is easy. Tomorrow, we'll look at how angular motion and linear motion affect each other and also add in a third acceleration value - centripetal acceleration - which is what promotes the circular motion to begin with.

Physics B reviewed their Machines and Efficiency math packet and addressed any final issues before tomorrow's exam. Physics F, on the other hand, conducted two lab investigations centering around conservation of energy. The motion of a basketball tossed into the air was used to corroborate conservation of energy and conversion of energy between kinetic and gravitational potential forms. A second experiment with a mass-spring system focused on kinetic and elastic potential energy. Some groups still have a bit to do on that last one, so there will be time provided in class on Monday to complete the work.

Physical Science reviewed their MCAS practice material for forces, laws of motion and momentum until they were called down for Peer Mentors. We'll continue to review the packet on Friday and start a general review of the material for this unit looking towards Tuesday for the unit exam.

Homework

Honors Physics: 7.1 Section Review and Practice 7D
Physics B and F: None
Physical Science: None

Momentum, Energy and Stuff

Honors Physics endured their momentum exams and will start a new unit tomorrow - rotational motion. Everything we've talked about so far has occurred in a linear model, now, we add in what happens when something rotates or revolves. Remember to set those calculators to work with angles in radians and light a small candle to the saint of the unit circle, because we're playing in that pool for the next two chapters...

Physics B and F worked on math practice for work, power, energy and simple machines. B block will go over these problems tomorrow and tie up any loose ends before Thursday's exam. F Block will go over these over the next two days, as time permits, while also working through a conservation of energy lab and having no class period on Thursday due to parent-teacher conferences.

Physical Science worked practice problems for conservation of momentum, which we went over in class and then began MCAS practice for forces, laws of motion and momentum. We'll go over that material tomorrow in class and talk about strategies for the MCAS exam that is looming in June.

Homework

Honors Physics: Complete the lab write up for yesterday's investigation
Physics B: Complete Machines and Efficiency math packet
Physics F: Have Machines and Efficiency math packet completed by Friday
Physical Science: Complete MCAS review packet

Momentum

Honors Physics conducted a lab investigation on momentum and kinetic energy conservation for different types of collisions. Students modeled elastic, perfectly inelastic and inelastic collisions and tracked momentum and energy changes for each type. The lab write up is due Wednesday since tomorrow is test day!

Physics B and F reviewed material for the momentum exam, which is scheduled for Thursday for B block and Friday for F block. Time was also taken to review the lab unit on simple machines. Not surprisingly, the machines behaved as they should - multiplying force or distance (but not both) and demonstrating IMA values greater than AMA values. tomorrow, math practice!

Physical Science reviewed conservation of momentum and worked some practice problems for the topic. Tomorrow, more practice and then practice on force and momentum problems for MCAS.

Homework

Honors Physics: Prepare for exam. Lab write up due on Wednesday
Physics B and F, Physical Science: None

Machines

Physics B and F began their lab unit on machines. The inclined plane, all three classes of simple levers and various pulley configurations will be tested for efficiency, actual mechanical advantage and ideal mechanical advantage. Students will also get a good chance to really see how these machines function to make work easier. Pretty much every group finished or nearly finished the inclined plane portion, so levers should be on the docket tomorrow. For inclined planes, it was quite clear that the effort force was less than the output force (weight of the load), but amount of work input was greater than the work output. Such is the cost of using a machine...

Honors Physics completed their discussion of impulse and momentum and we took time to review the lab and go over the impulse-momentum homework problems. Attention then turned to one of the biggies in physics - the law of conservation of momentum. The total momentum of a system remains constant in the absence of outside forces. Whatever momentum is lost by one object, that momentum is gained by someone else and vice versa. We discussed how conservation of momentum is mandated by Newton's 3^rd Law of Motion, which can be extended to say that the impulse experienced by two objects in a collision are equal in magnitude, but opposite in direction. We'll look at momentum conservation more tomorrow, before moving on to types of collisions.

Physical Science went over their impulse-momentum problems and it was clear that a little more work was needed. So, students have to create their own worksheet for momentum and impulse-momentum problems, script an answer key and be prepared to share their worksheet with others tomorrow in class.

Homework

Honors Physics: Practice 6D and the 6.2 Section Review #2, 4
Physics B and F: None
Physical Science: Self-created momentum and impulse-momentum worksheet and answer key

The Funny Thing Is...

...young Wookies are called "pups."

Monday

That single word is enough to cripple the spirits of any individual...

Honors Physics went over their work and energy exams and then launched into a discussion of impulse and momentum. FΔt = Δp describes the action of an impulse on an object's momentum and also nicely spotlights the role of time. Newton's 2^nd Law of Motion sometimes doesn't emphasize the role of time, as it gets hidden in the acceleration variable. But duration of force application is as important to changing an object's momentum as the force's magnitude. We discussed the idea of follow-through in sports and will highlight other examples of the role of time in tomorrow's class. Have your labs and 5A, 5B ready for tomorrow. We'll discuss the lab (which we already started doing today) and review those problems before moving on to conservation of momentum.

Physics B and F reviewed the six simple machines and how they function to make work easier. We then introduced the ideas of mechanical advantage and efficiency, which will be targeted heavily in the lab unit that we begin tomorrow. We'll look at inclined planes, all three classes of levers and pulleys (simple, movable and pulley-systems.) You'll calculate IMA and measure AMA to evaluate the machine's efficiency and also get a better look at how these machines manipulate force or distance to make work easier.

Physical Science went over their lab investigations in class and used them as an example to reintroduce the Impulse-Momentum theorem. We took time to review this idea before plunging headlong into some examples of this is mathematically applied. After we went over a couple of practice problems, students were given a sheet with additional samples to work. We'll go over these in class tomorrow before turning attention to conservation of momentum.

Homework

Honors Physics: None
Physics B and F: Complete Work and Energy review packets
Physical Science: Complete Impulse-Momentum practice problems

Honors Physics - This One's For You

Rain, Rain Go Away

Today's rain has pretty much set the stage for people's mood and energy level. Tomorrow, likely more of the same.

Honors Physics completed their impulse-momentum lab, which we will discuss tomorrow. The unit that the lab introduced, momentum and its conservation, builds on our work with forces, Newton's laws of motion and work to investigate another major physics concept. We'll tackle the impulse-momentum theorem, conservation of momentum and types of collisions before the unit is completed.

Physics B went over their Energy and Machines math packet before turning attention to the idea of machines. Yesterday's discussion of conservation of energy definitely applies to machines in that no machine can give you more work out that you put in. We began to look at the inclined plane family today and will continue with that and hit the lever family tomorrow. Then, we start a series of investigations with the simple machines. Physics F completed their material on the simple machines today and are ready to start lab work with conservation of energy and machines tomorrow.

Physical Science spent yesterday going over their momentum problems. Always remember to identify information, write down the formula and place information in the formula according to the variable it represents before just trying to punch numbers into the calculator. Also, you can never forget about those unit conversions. Today, students worked on a lab centering on momentum and how both mass and velocity affect an object's momentum. We'll discuss the lab tomorrow and start working some problems for the impulse-momentum theorem.

Homework

Honors Physics: Complete lab write up
Physics B and F: None
Physical Science: Complete lab write up

What Happens When You Spend All Day in the Patent Office

There Will Be Awesomeness

Shakespeare Goes Sci-fi in Michael Caine's Post-apocalyptic Henry5

Weak Monday

With the field trip today and a slew of general absences, classes were a little light on attendance. No matter, we'll catch people up tomorrow.

Honors Physics took their work and energy exam today and will leap into momentum on Wednesday with a lab on the impulse-momentum theorem. Interested people can read ahead in Chapter 6, but the lab does a good job on its own introducing the concept and letting you work with the math behind the idea.

Physics B, with a rocking total of 3 people, conducted two lab investigations, both of which targeted energy and its conservation. One lab looked at gravitational potential and kinetic energies and the second targeted kinetic and elastic potential energies. The lab nicely showed that regardless of how energy was divided up between the players, the total value remained constant. We'll go over the lab on Wednesday and take time to discuss kinetic and elastic potential energy in more depth.

Physics F discussed kinetic energy and elastic potential energy in class and got some practice with the problem solving for the various energy types and conservation of energy. We'll go over conservation of energy and review these problems in class tomorrow.

Physical Science went over their forces math quiz and were introduced to the concept of and formula for momentum. Remember not to confuse momentum with inertia - all mass has inertia, but only mass in motion has momentum. We'll go over the homework problems in class tomorrow before digger deeper into momentum and its conservation. The solutions to the homework problems can be found here.

Homework

Honors Physics: None
Physics B: Complete lab write up
Physics F: Complete Energy and Machines math packet
Physical Science: Complete Momentum math packet