Question

The free end of a simple pendulum is attached to the ceiling of a box. The box is taken to a height and the pendulum is oscillated. When the bob is at its lowest point, the box is released to fall freely. As seen from the box during this period, the bob will
(a) continue its oscillation as before
(b) stop
(c) will go in a circular path
(d) move on a straight line.

Answer 1

Answer ⇒ Option (c). Will go in the Circular Path.

Explanation ⇒  When the box is released from the bob, it was at its means position. This means, its velocity was maximum.

Now, if one observes from the box, then it is in non-inertial frame of reference.

Thus we will apply a pseudo force upwards. Now, the weight of the pendulum will be acting downwards.  The Pseudo Force will cancel the effect of the Gravity. Thus, it is observed that there will be no net force acting on the bob.

But, bob was having maximum velocity at this position thus, if no net force is there, then as per as newton's law of motion, it will continue to move with same velocity, thus acquiring the circular path.

Hence, Option (c). is correct.

Hope it helps.