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Unformatted text preview: ConcepTest ConcepTest 9.1 9.1 Rolling in the Rain Rolling in the Rain 1) speeds up 1) speeds up 2) maintains constant speed 2) maintains constant speed 3) slows down 3) slows down 4) stops immediately 4) stops immediately An open cart rolls along a frictionless track while it is raining. As it rolls, what happens to the speed of the cart as the rain collects in it? (assume that the rain falls vertically into the box) Since the rain falls in vertically, it adds no momentum to the box, thus the boxs momentum is conserved. However, since the mass of the box slowly increases increases with the added rain, its velocity has to decrease decrease . ConcepTest ConcepTest 9.1 9.1 Rolling in the Rain Rolling in the Rain 1) speeds up 1) speeds up 2) maintains constant speed 2) maintains constant speed 3) slows down 3) slows down 4) stops immediately 4) stops immediately An open cart rolls along a frictionless track while it is raining. As it rolls, what happens to the speed of the cart as the rain collects in it? (assume that the rain falls vertically into the box) Followup: Followup: What happens to the cart when it stops raining? What happens to the cart when it stops raining? A net force of 200 N acts on a 100kg boulder, and a force of the same magnitude acts on a 130g pebble. How does the rate of change of the boulders momentum compare to the rate of change of the pebbles momentum? 1) greater than 2) less than 3) equal to ConcepTest ConcepTest 9.3a 9.3a Momentum and Force Momentum and Force A net force of 200 N acts on a 100kg boulder, and a force of the same magnitude acts on a 130g pebble. How does the rate of change of the boulders momentum compare to the rate of change of the pebbles momentum? 1) greater than 2) less than 3) equal to The rate of change of momentum is, in fact, the force. Remember that F = p / t . Since the force exerted on the boulder and the pebble is the same, then the rate of change of momentum is the same....
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This note was uploaded on 05/13/2010 for the course PHYSICS 53L taught by Professor Mueller during the Fall '07 term at Duke.
 Fall '07
 Mueller
 Physics, Friction

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