A : When a rigid body rotates about any fixed axis, then all the particles of it move in circles of different radii but with same angular velocity.
R : In rigid body relative position of particles are fixed.

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 analyze the statements given in the question, we need to evaluate both the Assertion (A) and the Reason (R) to determine their validity and whether R correctly explains A.

### Step-by-Step Solution:

1. **Understanding the Assertion (A)**:
- The assertion states that when a rigid body rotates about a fixed axis, all particles of the body move in circles of different radii but with the same angular velocity.
- This is true because in rotational motion, every point in a rigid body rotates about the axis of rotation. While the distances (radii) from the axis may vary for different particles, they all share the same angular velocity (ω).

2. **Understanding the Reason (R)**:
- The reason states that in a rigid body, the relative positions of the particles are fixed.
- This is also true; in a rigid body, the distances between any two particles do not change during motion. This means that the shape and size of the body remain constant, which is a defining characteristic of a rigid body.

3. **Evaluating the Relationship between A and R**:
- The assertion (A) is correct, as explained. The reason (R) is also correct, as it describes a fundamental property of rigid bodies.
- To determine if R is the correct explanation for A, we need to see if the fixed relative positions of particles (R) directly support the idea that they can rotate in circles of different radii with the same angular velocity (A).
- Yes, the fixed relative positions imply that the distances from the axis of rotation can vary, allowing for different radii while maintaining the same angular velocity.

4. **Conclusion**:
- Both the assertion (A) and reason (R) are correct, and R correctly explains A. Therefore, the answer is that both A and R are true, and R is the correct explanation for A.

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

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