Prompt: On a frictionless horizontal air table, puck A (with mass 0.252 kg ) is

Question

Prompt: On a frictionless horizontal air table, puck A (with mass 0.252 kg ) is moving toward puck B (with mass 0.368 kg ), which is initially at rest. After the collision, puck A has velocity 0.119 m/s to the left, and puck B has velocity 0.647 m/s to the right.

Question:

1. What was the speed vAi of puck A before the collision? I got 0.826m/s which is correct!

2. Calculate K, the change in the total kinetic energy of the system that occurs during the collision. The answer should be .00712J. Could you tell me how to get that? My work isnt giving me that answer!

Explanation / Answer

Conservation of momentum

m1v1+m2v2=m1,fv1f+m2,fv2,f

m1=0.252 kg

m2= 0.368kg

v1,f=-0.119m/s

v2,f= 0.647 m/s

v1= ?

Putting all the values we get

v1=0.826m/s

Part(2);

Initial K.E=1/2mv2

=(0.5)(0.252)(0.826)2

=0.08596J

Final K.E=(0.5)(0.252)(0.119)2+0.5(0.368)(0.647)2

=0.00178+0.0770

=0.0788J

E= final- initial

=0.0788-0.08594

=-0.00713J

  (19)

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