Assertion `:-` The mechanical energy of earth-moon system remains same when a another heavenly body passes nearby the earth`-`moon system.
Reason `:-` Force exerted by heavenly body on the earth`-`moon system is non`-`conservative.

Options

A. If both Assertion & Reason are True & the Reason is a correct explanation of the Assertion.
B. If both Assertion & Reason are True but Reason is not a correct explanation of the Assertiion.
C. If Assertion is True but the Reason is False.
D. If both Assertion & Reason are False

Answer

To analyze the assertion and reason provided in the question, we will break down the concepts involved step by step.

### Step 1: Understand the Assertion
The assertion states that the mechanical energy of the Earth-Moon system remains the same when another heavenly body passes nearby.

**Explanation**:
- The mechanical energy of a system is the sum of its potential energy and kinetic energy.
- In the case of the Earth-Moon system, the gravitational interaction between the Earth and the Moon primarily determines its mechanical energy.
- When another heavenly body passes nearby, it can exert a gravitational force on both the Earth and the Moon, potentially altering their velocities and positions, which can lead to changes in the mechanical energy of the system.

### Step 2: Understand the Reason
The reason states that the force exerted by the heavenly body on the Earth-Moon system is non-conservative.

**Explanation**:
- A conservative force is one where the work done by the force on an object moving between two points is independent of the path taken. Gravitational forces are typically considered conservative.
- However, when another body passes nearby, it can create a varying gravitational field, which can lead to energy being transferred into or out of the Earth-Moon system. This indicates that the forces involved are not conservative in the context of the Earth-Moon system.

### Step 3: Evaluate the Assertion and Reason
- Both the assertion and the reason are false.
- The assertion is false because the mechanical energy of the Earth-Moon system does not remain the same when another body passes nearby; it can change due to the interaction.
- The reason is also false because the force exerted by the heavenly body can be considered conservative in a broader sense, but in this specific scenario, it leads to a change in energy.

### Conclusion
Both the assertion and the reason are false, which leads us to conclude that the correct answer is option D.

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