A magnet is dropped down an infinitely long vertical copper tube

Options

A. the magnet moves with continuously decreasing velocity and ultimately comes to rest
B. the magnet moves with continuously increasing velocity and ultimately acquires a constant temrinal velocity
C. the magnet moves with continuously increasing velocity and acceleration
D. the magnet moves with continuously increasing velocity but constant acceleration.

Answer

B

Explanation

Due to the relative motion between the magnet and the copper tube an eddy current is induced in the copper tube which opposes the motion of the magnet (Lenz.s law). This opposing force increases with the increases in velocity of the magnet as it falls down under gravity. ultimately, the opposing force balances the weight of the magnet and then no net force acts on the magnet and the magnet falls with a constant terminal velocity.