On a frictionless horizontal air table, put k A (with mass 0.249 kg) is moving t

Question

On a frictionless horizontal air table, put k A (with mass 0.249 kg) is moving toward puck B (with mass 0.375 kg), which is initially at rest. After the collasion, puck A has velocity 0.125 m/s to the left, and puck B has velocity 0.646 m/s to the right. What was the speed v_ of puck A before the collision? If you are required to use the answer obtained for a subsequent hint or part. Use your unrounded/full precision answer Calculate Delta K, the change in the total kinetic energy of the system that occurs during the collision

Explanation / Answer

A)
given

mA = 0.249 kg

mB = 0.375 kg

VBi = 0

after collision

vAf = -0.125 m/s

vBf = 0.646 m/s

vAf = ?

A) Apply conservation of momentum

mA*vAi + mB*Vbi = mA*vAf + mB*vBf

0.249*vAi + 0 = 0.249*(-0.125) + 0.375*0.646

vAi = 0.211125/0.249

= 0.858 m/s

B ) delta_KE = KEf - KEi

= 0.5*mA*vAf^2 + 0.5*mB*vBf^2 - 0.5*mA*VAi^2

= 0.5*0.249*0.125^2 + 0.5*0.375*0.646^2 - 0.5*0.249*0.848^2

= -9.03*10^-3 J

negative sign indicates final kinetic energy is lesss than initial kinetic energy.

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