When a body is whirled in a circle, the work done on it is

Options

A. positive
B. negative
C. zero
D. infinite

Answer

To determine the work done on a body that is whirled in a circle, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Motion**:
- When a body is whirled in a circle, it undergoes circular motion. The body moves along a circular path with a constant radius.

2. **Identifying the Forces**:
- In circular motion, a centripetal force is required to keep the body moving in a circle. This force acts towards the center of the circular path.

3. **Direction of Velocity and Force**:
- At any point in the circular path, the velocity of the body is tangent to the circle, while the centripetal force is directed towards the center of the circle.

4. **Calculating Work Done**:
- The formula for work done (W) is given by:
\[ W = F \cdot s \cdot \cos(\theta) \]
where \( F \) is the force, \( s \) is the displacement, and \( \theta \) is the angle between the force and the displacement.

5. **Analyzing the Angle**:
- In circular motion, the angle \( \theta \) between the centripetal force (which points towards the center) and the displacement (which is tangent to the circle) is always \( 90^\circ \).

6. **Using Cosine of the Angle**:
- The cosine of \( 90^\circ \) is \( 0 \):
\[ \cos(90^\circ) = 0 \]
- Therefore, substituting this into the work done formula gives:
\[ W = F \cdot s \cdot 0 = 0 \]

7. **Conclusion**:
- Since the work done is calculated to be zero, we conclude that the work done on a body that is whirled in a circle is **zero**.

### Final Answer:
The work done on a body that is whirled in a circle is **0**.

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