Question

On a frictionless horizontal air table, puck A (with mass 0.245 kg ) is moving toward puck B (with mass 0.374 kg ), which is initially at rest. After the collision, puck A has velocity 0.118 m/s to the left, and puck B has velocity 0.655 m/s to the right.

A: What was the speed vAi of puck A before the collision?

B: Calculate ΔKΔKDeltaK, the change in the total kinetic energy of the system that occurs during the collision.

Answer 1

Let m1, m2 be the two masses which has initial velocity v1 and v2 and velocities v1' and v2' after collision

a) By the principle of conservation of momentum we must have

m2 is at rest initially i.e., v2=0

Also we have

here we have assume right to be positive and left to be negative

Putting the values,

b) Initially only A has velocity and hence kinetic energy

After collision both A and b has kinetic energy given by

So, change in kinetic energy is

The minus sign indicates that there is a loss in kinetic energy after the collision took place

So, magnitude of the loss in kinetic energy is 0.013 J