Question

On a frictionless horizontal air table, puck A (with mass 0.245 kg ) is moving toward puck B (with mass 0.373 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 0.647 m/s to the right.

a. What was the speed vAi of puck A before the collision?

b. Calculate ΔK, the change in the total kinetic energy of the system that occurs during the collision.

Answer 1

Solution

Data

a) To resolve this part o the proble, we use the lineal momentum conservation for both pucks:

(1)

(2)

Where;

v_iA: is the speed of the puck A before the collision

v_iB: is the speed of the puck A before the collision

u_fA: is the speed of the puck A after the collision

u_fB: is the speed of the puck B after the collision

Now matching the horizontal components

(3)

Now, clearing v_iA, we have:

(4)

Substituting the values

Then, the speed of puck A before the collision is:

b) In this part of the problem, we first find the kinetic energy of the system before and after the collision

Before the collision

(5)

After the collision

(6)

Then, the change in total kinetic energy is the difference in the kinetic energy of the system after the collision and before the collision

(6)

So, the chamge in the total kinetic energy of the system is: