Rolling Along

Honors Physics reviewed one last problem for rotational equilibrium before moving into examining how torque can upset or produce equilibrium through generating angular acceleration. When working with Newton’s 2nd Law for rotational systems, make sure to choose the right shape when picking your moment of inertia formula. The same holds for your calculations with angular momentum and kinetic energy. For angular momentum, we should have a bit of time tomorrow to allow you to experience conservation of angular momentum (provided we complete going over homework problems in time). Exam will fall preferably Tuesday of next week, or possibly Wednesday. Let’s see how the next few days go with machines…

Physical Science B worked on practice problems dealing with conservation of mechanical energy. Yes, I know they were tough…they are supposed to be tough. The only way to learn to work problems is to work many of them and don’t always stick to the easy type. These have you work your brain a bit to figure out how to pull all of the elements of the problem together, but they still really on only two formulas – GPE and KE. Remember, too, that you are only responsible for problems 1-5. We’ll go over them tomorrow and make sure that we are clear on energy and its conservation before moving on to efficiency in machines.

Physical Science E reviewed their conservation of energy lab and then dived deeper into the law of conservation of energy both in concept and in calculation. Tomorrow, you will get some practice problems for conservation of energy that you will work on in class. The problem on which you are working tonight will be useful practice for the set that you’ll tackle tomorrow.

Physics F and G began their study of torque. Torque, the ability of a force to produce rotation, is responsible for the angular accelerations that we calculated in the last chapter. We discussed the effect of force and lever arm on the magnitude of torque and will talk later about how machines use torque to do work. Remember to pay attention to the sign of torque – counterclockwise is positive and clockwise is negative – when working problems. Take some time tonight to look around your house for examples of torque in action. Think about lever arm and how that might explain how some devices work/are constructed.

Homework

Honors Physics A: Practice 8D and 8E
Physical Science B: Complete conservation of energy practice problems
Physical Science E: Solve the following problem:

A boy drops a 1.7 g penny from a window that is 12 meters above the sidewalk. At what speed does the penny hit the sidewalk?

Physics F and G: Complete the torque worksheet