General Physics 2, Spring '10

Homework 4

Let's make a deal. I'll give you fewer homework problems, and you spend a little extra time writing up the solutions in a way that is more clear, neat, legible, organized, readable, presentable,...

1. Pick one of the Questions for Thought and Discussion (not the Projects!) to contemplate and answer.

2. Work through the falling yo-yo problem from Monday's class: the yo-yo has radius R, mass M, and moment of inertia I, and is unwinding downward; your job is to find its acceleration. We did this in class already using energy conservation. So you should do it using torque and angular momentum. You may choose the origin of your coordinate system anywhere you want; just be explicit about what you're doing. (There are two places you might choose that will make this very similar to the worked example in the text; if you're feeling ambitious/curious you might try putting it somewhere else and showing that you still get the right answer out at the end.)

3. Project 4.5. Hint: if the platform/board is going to be in equilibrium, not only must the net force vanish, but the net torque must also vanish.

4. Several of the Projects for this chapter (e.g., 4.4, 4.11, 4.12) presuppose that you know calculus. If you do know calculus, pick one of those to work out. If not, do Project 4.13 (which requires no calculus).