The two sleds shown below are about to collide. When they collide, they bounce off each other and no energy is lost. The kinetic energy of sled A is 39,561 J just after the collision. What is the kinetic energy of sled B after the collision? (Note: The potential energy of each sled after the collision is 0 J.)

Explanation:
Given that,
The potential energy of the slides before collision are
U_a = 13,700 J
U_b = 32,300 J.
Also, the final potential energy of sled B is
V_b = 39,561 J
So, since the body bounce off after collision, then it is elastic collision and in elastic collision, energy is conserved.
So, applying conservation of energy and since no energy is loss, then, total potential energy before collision is equal to total potential energy after collision.
Then,
U_a + U_b = V_a + V_b
13,700 + 32,300 = V_a + 39,561
Then,
V_a = 13,700 + 32,300 - 39,561
V_a = 6439