PL W8 1.Mon-answers (All Correct) University of Cincinnati, Main Campus PHYSICS 2001

PL W8 Mon Reading: Chapter 9, sections 9.1, 9.2, and 9.3. Lecture Videos: Lecture 9A: Impulse and Momentum Lecture 9B: Impulse and Momentum in 2D Questions from the first video lecture (Impulse and Momentum) 1. Two eggs are dropped from equal heights. One falls onto a concrete block and the other falls on a pillow. The egg that hits the concrete block breaks, but the one that hits the pillow does not. Why? A. The pillow absorbs energy so the egg on the concrete has more energy for breaking it. B. The pillow makes the egg bounce, so that egg keeps some of its momentum and doesn’t have enough energy to break. C. The collision with the pillow lasts a longer time than the collision with the concrete, so there is less force on the egg that hits the pillow. D. The egg that goes into the pillow falls a longer distance so its momentum does not change as much as it gets less impulse. Answer: C 2. A clay ball and a superball that have the same mass and same velocity are flying toward equal wooden blocks. The clay ball sticks to its block, and the superball bounces off its block with very little loss of kinetic energy. Which ball is most likely to cause the block to tip over? A. The block hit by the clay ball is more likely to fall. B. The block hit by the superball is more likely to fall. C. Both blocks are equally likely to fall. D. More information is needed. Answer: B Here is a great (1 min) video that shows experimentally which ball is more likely to tip the block over: Additional questions to test your understanding 3. Two identical bullets are fired horizontally with identical speeds v0 at two blocks of equal mass. The blocks rest on a frictionless horizontal surface and are made of hard steel and soft wood, respectively. One bullet bounces elastically off the steel block. The other bullet becom