A 5-kg object is moving to the right at 4 m/s and collides with a 4-kg object moving to the left at 5 m/s.The objects collide and stick together.After the collision,the combined object:
A)has the same kinetic energy that the system had before the collision.
B)has more kinetic energy than the system had before the collision.
C)has no kinetic energy.
D)has less momentum than the system had before the collision.

Question

Quizplus · Accepted Answer

After the collision, the objects stick together, which means they move with a combined velocity of 0 m/s. This means there is no kinetic energy because KE = 1/2mv^2 where v = 0. Additionally, conservation of momentum tells us that the total momentum before the collision is equal to the total momentum after the collision. Therefore, the combined object has the same momentum as the system before the collision. It does not have less momentum (choice D) nor more kinetic energy than before (choice B).

A 5-Kg Object Is Moving to the Right at 4