Which of the following cannot be used for measuring time in a spaceship orbiting around the earth?

Options

A. Atomic clock
B. Quartz watch
C. Electric clock
D. Pendulum clock

Explanation

To determine which of the following cannot be used for measuring time in a spaceship orbiting around the Earth, we need to analyze the timekeeping mechanisms of different types of clocks.

### Step-by-Step Solution:

1. **Understanding the Environment**:
- In a spaceship orbiting Earth, the conditions are different from those on the surface. The spaceship is in a state of free fall, which creates a microgravity environment. This means that the effective gravitational acceleration (G) is approximately zero.

2. **Analyzing Different Clocks**:
- **Atomic Clock**:
- An atomic clock measures time based on the vibrations of atoms. It does not rely on gravitational force (G) to function. Therefore, it can be used in a spaceship.
- **Quartz Clock**:
- A quartz clock operates using an electronic oscillator regulated by a quartz crystal. Similar to the atomic clock, it does not depend on gravitational force and can function accurately in a microgravity environment.
- **Electrical Clock**:
- An electrical clock is powered by electricity and does not rely on gravitational force for its operation. Thus, it can also be used in a spaceship.
- **Pendulum Clock**:
- A pendulum clock measures time based on the swinging motion of a pendulum, which is directly affected by gravity. The formula for the time period of a pendulum is given by \( T = 2\pi \sqrt{\frac{L}{g}} \), where \( L \) is the length of the pendulum and \( g \) is the acceleration due to gravity. In a microgravity environment (where \( g \approx 0 \)), the time period \( T \) approaches infinity, making it ineffective for measuring time.

3. **Conclusion**:
- The pendulum clock cannot be used for measuring time in a spaceship orbiting around the Earth because it relies on gravitational force for its operation, which is absent in that environment.

### Final Answer:
The pendulum clock cannot be used for measuring time in a spaceship orbiting around the Earth.

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