On a frictionless horizontal air table, puck A (with mass 0.247 kg) is moving to

Question

On a frictionless horizontal air table, puck A (with mass 0.247 kg) is moving toward puck B (with What was the speed VAi of puck A before the collision? mass 0.369 kg), which is initially at rest. After the collision, puck A has velocity 0.120 m/s to the left, and puck B has velocity 0.648 m/s to the right. What was the speed upsilon_Ai of puck A before the collision? upsilon_Ai = 0.84 m/s Correct If you are required to use the answer obtained for a subsequent hint or part, use your unrounded/full precision answer. Part B calculate DeltaK, the change in the total kinetic energy of the system that occurs during the collision.

Explanation / Answer

Part A :

According to the conservation of momentum,
m1v1 + m2v2 = m1v3 + m2v4
Set right as positive
0.247v1 = 0.247*(-0.120) + 0.369 *0.648
v1 = 0.848 ms^-1

Part B:

Initial kinetic energy = 0.247 *0.848^2 /2 = 0.178 J
Final kinetic energy = 0.247 *0.120^2 /2 + 0.369 *0.648^2 /2

= 0.0793 J
Thus, the total kinetic energy has decreased.

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