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## Homework 4

GenPhysI, Fall '10, Homework 4 (covering UP Chapter 3)

1. Problem 1 ("Stopping a Neutron")

2. Problem 18 ("Three Blocks")

3. Problem 34 ("Other-Worldly Pitch")

4. A fully loaded freight train moving at top speed rams into a hovering mosquito. Clearly the force exerted by the train on the mosquito (SPLAT!) is huge compared to the force the mosquito exerts on the train. Is this a violation of Newton's Third Law? Why or why not?

5. "Consider a ball that is thrown straight up in the air. At the moment it reaches its maximum height, its velocity -- and therefore also its acceleration -- is zero. But the acceleration being zero means that the velocity isn't changing, so the velocity should remain zero into the next moment... and so on forever. Therefore, if you throw a ball straight up, it'll reach some maximum height and then hover there in midair forever." Since we know from experience that this isn't what happens, it's clear that something is wrong with the argument in quotes. What precisely is wrong with it?

1. Problem 1 ("Stopping a Neutron")

2. Problem 18 ("Three Blocks")

3. Problem 34 ("Other-Worldly Pitch")

4. A fully loaded freight train moving at top speed rams into a hovering mosquito. Clearly the force exerted by the train on the mosquito (SPLAT!) is huge compared to the force the mosquito exerts on the train. Is this a violation of Newton's Third Law? Why or why not?

5. "Consider a ball that is thrown straight up in the air. At the moment it reaches its maximum height, its velocity -- and therefore also its acceleration -- is zero. But the acceleration being zero means that the velocity isn't changing, so the velocity should remain zero into the next moment... and so on forever. Therefore, if you throw a ball straight up, it'll reach some maximum height and then hover there in midair forever." Since we know from experience that this isn't what happens, it's clear that something is wrong with the argument in quotes. What precisely is wrong with it?

Last modified: Monday, December 19, 2011, 9:18 AM