A: When a bar magnet is dropped into a vertical long hollow metallic tube, the magnet ultimately moves with zera acceleration.
R: The magnet falling into metallic tube causes the eddy currents in the metal tube, so the motion of the magnet is damped.

Options

A. If both Assertion & Reason are true and the reason is the correct explanation of the assertion.
B. If both Assertion & Reason are true but the reason is not the correct explanation of the assertion.
C. If Assertion is true statement but Reason is false.
D. If both Assertion and Reason are false statements.

Answer

To solve the assertion and reason question regarding the behavior of a bar magnet dropped into a vertical hollow metallic tube, we can break down the explanation into clear steps:

### Step-by-Step Solution:

1. **Understanding the Situation**:
- A bar magnet is dropped into a long vertical hollow metallic tube.

2. **Magnetic Flux Change**:
- As the bar magnet falls, it creates a changing magnetic field around it. The magnetic field lines from the magnet pass through the metallic tube, and as the magnet moves, the amount of magnetic flux linked with the tube changes.

3. **Induction of Eddy Currents**:
- According to Faraday's law of electromagnetic induction, a change in magnetic flux induces an electromotive force (EMF) in the conductor (the metallic tube). This induced EMF causes currents to flow in the tube, known as eddy currents.

4. **Direction of Eddy Currents**:
- By Lenz's law, the direction of the induced eddy currents will be such that they oppose the change in magnetic flux that produced them. In this case, the eddy currents will create a magnetic field that opposes the falling magnet.

5. **Resulting Forces**:
- The eddy currents generate a magnetic force that acts upwards against the motion of the falling magnet. This force is a retarding force that opposes the weight of the magnet.

6. **Terminal Velocity**:
- As the magnet continues to fall, its velocity increases, which in turn increases the induced eddy currents and the opposing force. Eventually, the upward magnetic force due to the eddy currents becomes equal to the downward gravitational force (weight) acting on the magnet.

7. **Zero Acceleration**:
- When these forces balance each other, the net force acting on the magnet becomes zero. At this point, the magnet continues to fall but at a constant terminal velocity, meaning it has zero acceleration.

8. **Conclusion**:
- Therefore, the assertion that the magnet ultimately moves with zero acceleration is true. The reason that the falling magnet causes eddy currents in the tube, which dampens its motion, is also true. Thus, both the assertion and the reason are correct, and the reason provides a correct explanation for the assertion.

### Final Answer:
Both the assertion (A) and the reason (R) are true, and R is the correct explanation for A.

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