When a man walks on a horizontal surface with constant velocity work done by the

Options

A. frictional force is zero
B. contact force is zero
C. gravity is zero
D. man is zero

Answer

To solve the question regarding the work done by a man walking on a horizontal surface with constant velocity, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Scenario**:
- The man is walking on a horizontal surface with a constant velocity. This implies that there is no change in speed or direction.

2. **Identify Initial and Final Velocities**:
- Since the man is walking with constant velocity, we can denote his initial velocity (u) and final velocity (v) as equal:
\[ u = v \]

3. **Calculate Acceleration**:
- Using the equation of motion, \( v = u + at \), we can rearrange it to find acceleration (a):
\[ a = \frac{v - u}{t} \]
- Substituting \( v = u \):
\[ a = \frac{u - u}{t} = \frac{0}{t} = 0 \]
- Therefore, the acceleration of the man is zero.

4. **Determine the Force Acting on the Man**:
- According to Newton's second law, force (F) is given by:
\[ F = m \cdot a \]
- Since we found that \( a = 0 \):
\[ F = m \cdot 0 = 0 \]
- Thus, the net force acting on the man is zero.

5. **Calculate Work Done**:
- Work done (W) is calculated using the formula:
\[ W = F \cdot d \]
- Where \( d \) is the displacement. Since the force \( F = 0 \):
\[ W = 0 \cdot d = 0 \]
- Therefore, the work done by the man is zero.

6. **Conclusion**:
- The correct answer is that the work done by the man while walking with constant velocity on a horizontal surface is zero.

### Final Answer:
The work done by the man is **0**.

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