In an elastic collision of two billiard balls, the total kinetic energy is conserved?
A.
Completely
B.
For a short duration
C.
For a long duration but not completely
D.
None of Above
Answer: Option B
Explanation:
During the short time of collision when the balls are in contact, the kinetic energy of the balls gets converted into the potential energy. In an elastic collision, though the kinetic energy before the collision is equal to the kinetic energy after the collision but kinetic energy is not conserved during the short time of collision.
Which of the following is an example for a force which does work on a body but fails to change its kinetic energy?
A.
A body pulled through a plain surface
B.
A body pulled through a vertical surface
C.
A body pulled through a horizontal surface
D.
A body at rest
Answer: Option C
Explanation:
When a body is pulled through a rough horizontal surface with constant velocity, work is done by the applied force on the body but the kinetic energy of the body remains unchanged.
