A 44-kg ice skater moves across the ice at a constant speed of 2.0 m/s. She is c

Question

A 44-kg ice skater moves across the ice at a constant speed of 2.0 m/s. She is caught by her 76-kg partner, and then the pair continues to glide together. He is at rest when he catches her, and immediately afterward they both coast. Even though the "magnitude of the change in momentum" is requested, you should provide a negative sign if the final momentum is less than (or more negative) than the initial momentum.

Part A: What is their velocity just after the catch? Assume she moves in the positive x-direction before her partner catches her.

Part B: A skater follows the girl at a constant speed of 1.0 m/s. What is the magnitude of the girl's change in momentum in the reference frame of the skater?

Please answer with units.

Explanation / Answer

part A

pbefore (pair) = 44*2+ 76*0 = 88kgm/s

p after (pair)= (44+76)v= 88 (law of conservation of momentum)

                    v = 0.73 m/s

part b

w r t the skater, girls speed, Vgs = 2-1 = 1m/s

initial momentum of girl wrt skater, Pgs = 44*1 = 44kgm/s

final momentum of girl wrt skater = 44(0.73-1) = -11.88 kgm/s

magnitude of the girl's change in momentum in the reference frame of the skater = -11.88-44 = -55.88 kgm/s

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