A bar magnet is released from rest along the axis of a very long, vertical copper tube. After some time the magnet.

Options

A. will come to rest in the tube,
B. will move with constant acceleration g.
C. will start oscillating along vertical line.
D. will acquire almost constant speed.

Answer

D

Explanation

Magnet first starts falling down under gravity. Induced current in the tube opposes the motion of magnet by applying magnetic force. If tube has sufficient length then after some time magnetic force becomes equal to weight of the magnet and then onwards magnet starts falling down with constant speed.