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Unformatted text preview: Solution for Longanswer Homework 6 Inertia and Momentum problems Solution to Longanswer Homework Problem 6.1() Problem: Two dogs are playing on an icy pond (you know eventually they are going to run into each other, right?). To the right is an xt graph of a collision between the two dogs . One dog has an inertia of 1kg (very similar to a standard cart). Dog 2 has inertia of 4kg . (a)What are the initial and final velocities of both dogs? (b)What are the changes in the velocities of both dogs? (c)Do these values satisfy equation 5 . 1 ? (d)Draw a vt graph for this collision. Does dog 1 ac celerate? If so, when, and what is the sign of the acceleration? What about dog 2 ? t 1 (s) 2 (s) x ( t ) 5 (m)3 (m) Dog 1 Dog 2 Collision (5,4) (m) Solution to Part (a) • V D 1 = x f − x i Δ t = 3m − ( − 3m) 1s = +6 m s • V D 1 f = x f − x i Δ t = − 1m − 3m 2s − 1 . 25s = − 4m . 75s = 5 . 3 m s The method for finding Dog Two‘s velocities is the same: • V D 2 = 4m − 5m 1s = 1 m s • V D 2 f = 5 . 4m − 4m 2s − 1 . 25s = 1 . 4m . 75s = 1 . 87 m s Grading Key: Part (a) 2 Points Solution to Part (b) Δ V D 1 = V D 1 f V D 1 = 5 . 3 m s 6 m s = 11 . 3 m s Δ V D 2 = V D 2 f V D 2 = 1 . 87 m s ( 1 m s ) = +2 . 87 m s Grading Key: Part (b) 2 Points Solution to Part (c) Eqt. 5 . 1 : M 2 M Std = Δ V Std Δ V 2 4kg 1kg = 11 . 3 m s 2 . 87 m s 4 = 3 . 9 OK,OK it’s not true but it should be, the error is a product of rounding... Grading Key: Part (c) 1 Points 1 Solution to Part (d) Yes, both dogs accelerate (they each experienced a nonzero change in velocity, so this is true). Dog 1 accelerates in the negative direction during the instant of the collision, in the time interval of 1s to 1 . 25s (Dog 2 accelerates in the same time of course, and in the positive direction). v t 8 1 2 4 6 7 5 3 1s 1.25s 2s Dog 2 Dog 1 Grading Key: Part (d) 5 Points Total Points for Problem: 10 Points Solution to Longanswer Homework Problem 6.2(Momentous Events) Problem: One hot summer day, you are cruising on your 1000kg chopper at a velocity of 30 m s when a huge bug splatters on the visor of your helmet. Before its tragic death, the monstrousbug splatters on the visor of your helmet....
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 Spring '08
 Stewart
 Physics, Acceleration, Inertia, Momentum, Work, Velocity, Longanswer Homework Problem

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