Question

A simple pendulum oscillates freely between points A and B.

We now put a peg (nail) at the point C as shown in above figure. As the pendulum moves from A to the right, the string will bend at C and the pendulum will go to its extreme point D. Ignoring friction, the point D

(a) will lie on the line AB

(b) will lie above the line AB

(c) will lie below the line AB

(d) will coincide with B

Answer 1

Answer is : (a) will lie on the line AB

Total length of a pendulum remains same, so extreme point D lies on the line AB, as shown below.

This can be proved by applying energy conservation between extreme positions A and D (its given friction is abscent),