The work done by a satellite in a complete orbit is

Options

A. infinity
B. unity
C. zero
D. negative

Answer

To solve the question regarding the work done by a satellite in a complete orbit, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Motion of the Satellite**:
- A satellite revolves around the Earth due to the gravitational force acting between the Earth and the satellite. This force acts towards the center of the Earth.

2. **Identifying the Forces**:
- The gravitational force \( F \) acting on the satellite can be expressed using Newton's law of gravitation:
\[ F = \frac{G \cdot M \cdot m}{r^2} \]
where \( G \) is the gravitational constant, \( M \) is the mass of the Earth, \( m \) is the mass of the satellite, and \( r \) is the distance between the center of the Earth and the satellite.

3. **Centripetal Force Requirement**:
- The gravitational force also acts as the centripetal force required for the satellite to maintain its circular motion. Thus, the satellite moves in a circular path with constant speed.

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

5. **Analyzing Displacement**:
- When the satellite completes one full orbit, it returns to its starting point. Therefore, the total displacement \( d \) for the satellite is zero (since the initial and final positions are the same).

6. **Conclusion on Work Done**:
- Since the displacement is zero, the work done by the gravitational force on the satellite during one complete orbit is:
\[ W = F \cdot 0 = 0 \]
- Thus, the work done by the satellite in a complete orbit is zero.

### Final Answer:
The work done by a satellite in a complete orbit is **0**.

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