A : When a man is walking on a rough road, that work done by frictiona force is zero.
R : Frictional force acts in the direction of the motion of the man in this case.

Options

A. If both Assertion & Reason are true and the reason is the correct explanation of the assertion, then mark (1).
B. If both Assertion & Reason are true but the reason is not the correct explanation of the assertion, then mark (2).
C. If Assertion is true statement but Reason is false, then mark (3).
D. If both Assertion and Reason are falsė statements, then mark (4).

Answer

To analyze the given statements, we need to evaluate both the assertion (A) and the reason (R) separately and then determine their truthfulness and relationship.

### Step 1: Understanding the Assertion (A)
The assertion states that "when a man is walking on a rough road, the work done by the frictional force is zero."

- **Explanation**: When a person walks, their foot pushes backward against the ground. According to Newton's third law, the ground exerts an equal and opposite frictional force forward on the foot. However, since the person is walking and not sliding, the displacement of the foot in the direction of the frictional force is zero.

- **Work Done Calculation**: Work done (W) is calculated using the formula:
\[ W = F \cdot d \cdot \cos(\theta) \]
where \(F\) is the force, \(d\) is the displacement, and \(\theta\) is the angle between the force and displacement vectors. In this case, since the displacement in the direction of the frictional force is zero, the work done by the frictional force is:
\[ W = F \cdot 0 \cdot \cos(\theta) = 0 \]
Thus, the assertion is **true**.

### Step 2: Understanding the Reason (R)
The reason states that "frictional force acts in the direction of the motion of the man in this case."

- **Explanation**: When the man walks, the frictional force does indeed act in the direction of his motion (forward). However, it is important to note that the frictional force acts in the opposite direction to the force exerted by the foot on the ground.

- **Direction of Forces**: The foot pushes backward, and the frictional force acts forward. Therefore, the frictional force does not act in the same direction as the man's motion; rather, it acts to oppose the backward push of the foot.

Thus, the reason is **false**.

### Step 3: Conclusion
- The assertion (A) is **true**.
- The reason (R) is **false**.

Therefore, the correct answer is that the assertion is true, but the reason is false.

### Final Answer
Assertion is true, Reason is false.

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