Physics 115 Test 2A with key


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Unformatted text preview: To keep the angular momentum at the same value: when rotational mass g oes down, ang ular speed must go up. Question 10 – You are driving your car down the highway and rounding a curve at constant speed. Are the car’s momentum and/or its kinetic energy constant? ( = constant, = not constant ) momentum kin etic ene rgy a. b. c. d. Answer (b) 2 momentum is a vector: mass x velocity, but kinetic energy is just a number : ½ x mass x spe ed . Because the velocity changes (the direction changes) but the speed doesn’t, momentum is not conserve d but kinetic energy is. PHYS115 – Spring 2013 5 Test 2 - 19 April 2013 Question 11 – You take the elevator from the 22nd floor to th 7th floor. Between the 8th and the 7th he o floor the elevator car slows down so it can stop at the 7th flo or. An accelerometer is mounted to the cei‐ ling of the car. Which picture shows the accelerometer betwe en the 8th and the 7th floor, where the car is slowing down? NOTE: Answer (d) is: “cannot tell because the speed is unkno wn”. (c) (b) (a) (d) Answer (d): Cannot tell because the speed is unknown v v v Answer (a) th th Between the 8 and the 7 floor the acceleration is up (its downward spee d decreases). Because the accelerometer’s block of...
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This document was uploaded on 02/23/2014 for the course PHYSICS 115 at UNL.

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