Assertion: Internal forces cannot change linear momentum.
Reason: Internal forces can change the kinetic energy of a system.

Options

A. (a) If both Assertion and Reason are true and the Reason is correct explanation of the Assertion.
B. (b) If both Assertion and Reason are true but Reason is not the correct explanation of Assertion.
C. (c) If Assertion is true, but the Reason is false.
D. (d) If Assertion is false but the Reason is true.

Explanation

To solve the question, we need to analyze the assertion and reason given:

**Assertion:** Internal forces cannot change linear momentum.
**Reason:** Internal forces can change the kinetic energy of a system.

### Step-by-Step Solution:

1. **Understanding Linear Momentum:**
- Linear momentum (P) of a system is defined as the product of its mass (m) and velocity (v), given by the equation P = mv.
- The principle of conservation of linear momentum states that if no external forces act on a system, the total linear momentum of the system remains constant.

2. **Analyzing the Assertion:**
- The assertion states that internal forces cannot change linear momentum. This is true because internal forces act between the components of a system and do not affect the overall momentum of the system.
- For example, if a mass M splits into two masses M1 and M2, the internal forces during the splitting do not change the total momentum of the system. If the system was initially at rest, the total momentum after the split will also be zero.

3. **Analyzing the Reason:**
- The reason states that internal forces can change the kinetic energy of a system. This is also true.
- When a system undergoes internal interactions (like splitting), the kinetic energy of the individual components can change. For instance, if the mass M splits into M1 and M2, the kinetic energy of M1 and M2 can be different from that of M.

4. **Connecting Assertion and Reason:**
- While both the assertion and reason are true, the reason does not provide a correct explanation for the assertion.
- The assertion focuses on linear momentum, while the reason discusses kinetic energy. The change in kinetic energy does not imply a change in linear momentum due to the conservation principle.

5. **Conclusion:**
- Therefore, the assertion is true, the reason is true, but the reason is not the correct explanation of the assertion.

### Final Answer:
Both the assertion and reason are true, but the reason is not the correct explanation of the assertion.

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