In order to find time, an astronant orbiting in an earth satellite should use

Options

A. A watch having flat spiral spring
B. pendulum clock
C. Neither pendulum clock nor a spiral spring clock
D. either pendulum clock or a spring clock

Answer

To solve the question regarding which timekeeping device an astronaut should use while orbiting in an Earth satellite, we need to analyze the options provided and understand the principles behind the timekeeping mechanisms.

### Step-by-Step Solution:

1. **Understanding the Options**:
- The options given are:
1. A watch having a flat spiral spring
2. A pendulum clock
3. Neither pendulum clock nor a spring clock
4. Either pendulum clock or a spring clock

2. **Analyzing the Pendulum Clock**:
- The time period \( T \) of a simple pendulum is given by the formula:
\[ T = 2\pi \sqrt{\frac{L}{g}} \]
where \( L \) is the length of the pendulum and \( g \) is the acceleration due to gravity.

3. **Effect of Gravity**:
- In a satellite orbiting the Earth, the astronaut experiences microgravity or weightlessness because they are in free fall. The effective gravitational force acting on the pendulum is significantly reduced, which means that the pendulum will not oscillate in the same manner as it would on the surface of the Earth.

4. **Analyzing the Spring Clock**:
- A watch with a flat spiral spring operates based on the tension in the spring and does not depend on gravitational force. The timekeeping mechanism is independent of gravity, making it suitable for use in a satellite.

5. **Conclusion**:
- Since a pendulum clock relies on gravity to function properly and will not work effectively in a microgravity environment, the correct choice for the astronaut would be a watch with a flat spiral spring. Therefore, the answer is:
- **A watch having flat spiral spring**.

### Final Answer:
The astronaut orbiting in an Earth satellite should use **a watch having a flat spiral spring**.