Which one of the following statements is true?

1. In an elastic collision of two bodies, the momentum, and energy of each body is conserved.
2. Total energy of a system is always conserved, no matter what internal and external forces on the body are present.
3. Work done in the motion of a body over a closed loop is zero for every force in nature.
4. Usually in an inelastic collision, the final kinetic energy is always less than the initial kinetic energy of the system.

Two identical ball bearings in contact with each other and resting on a frictionless table are hit head-on by another ball bearing of the same mass moving initially with a speed V. If the collision is elastic, which of the following figure is a possible result after collision?

1.  (i)

2.  (ii)

3.  (iii)

4.  None of these.

The bob A of a pendulum released from 30° to the vertical hits another bob B of the same mass at rest on a table as shown in the figure. How high does bob A rise after the collision? Neglect the size of the bobs and assume the collision to be elastic. 

1. Bob A will rise to a height of 0.01 m.
2. Bob A will rise to a height of 0.5 m.
3. Bob A will not rise at all.
4. Bob A will rise to a height of 0.3 m.

Which of the following potential energy curves can possibly describe the elastic collision of two billiard balls? Here r is the distance between the centres of the balls.

1. (i) and (iii)
2. (ii), (iii), and (iv)
3. (v) and (vi)
4. only (v)