Two masses collide and stick together. Before the collision one ...

[leo leo]

Two masses collide and stick together. Before the collision one of the masses was at rest. Is there a situation in which the kinetic energy is conserved in such a collision?
 a. Yes, if the less massive particle is the one initially at rest.
  b. Yes, if the more massive particle is the one initially at rest.
  c. Yes, if the two particles have the same mass.
  d. No, kinetic energy is always lost is such a collision.

Question 2

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.

[jackie]

Answer to Question 1

d

Answer to Question 2

c