Question

A bar magnet falls from a height 'h' through a metal pipe, its acceleration after coming out of pipe is

• A. less than \(9.8\text{ m/s}^2\)
• B. greater than \(9.8\text{ m/s}^2\)
• C. equal to \(9.8\text{ m/s}^2\)
• D. equal to 'h' \(\text{m/s}^2\)

Hint:

Eddy current braking stops once the magnet leaves the pipe.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
When a magnet falls through a metal pipe, the changing flux induces eddy currents in the pipe. By Lenz's law they oppose the motion, so the magnet falls slower than free fall while it is inside the pipe.

Step 2: After leaving the pipe:
Once the magnet has come out, there is no conductor around it. So there are no eddy currents and nothing opposes its fall. Only gravity acts.

Step 3: Result:
Its acceleration is \(g=9.8\ \text{m/s}^2\). Option (C). Less than \(g\) applies only inside the pipe, and more than \(g\) is never possible here.

Final Answer:
Outside the pipe the magnet is in free fall. \[ \boxed{9.8\ \text{m/s}^2} \]