Question

The bob A of a pendulum released from a height h hits head-on another bob B of the same mass of an identical pendulum initially at rest. What is the result of this collision? Assume the collision to be elastic.

• A. Bob A comes to rest at B and bob B moves to the left attaining a maximum height h.
• B. Bobs A and B both move to the left, each attaining a maximum height $\frac{h}{2}$.
• C. Bob B moves to the left and bob A moves to the right, each attaining a maximum height $\frac{h}{2}$.
• D. Both bobs come to rest.

Answer 1

The correct option is A

Bob A comes to rest at B and bob B moves to the left attaining a maximum height h.

Suppose bob A acquires a velocity v on reaching bob B. In a head-on elastic collision between two bodies of the same mass when one of them is at rest, the velocities are exchanged after the collision. Hence, bob A will come to rest at the lowermost position (occupied by B before collision) and bob B will move to the left attaining a maximum height h. Hence, the correct choice is (a).