Two earth-satellite are revolving in the same circular orbit round the centre of the earth. They must have the same

Options

A. mass
B. angular momentum
C. kinetic enrgy
D. velocity

Answer

To solve the question, we need to analyze the properties of two Earth satellites revolving in the same circular orbit around the center of the Earth.

### Step-by-Step Solution:

1. **Understanding the Problem**: We have two satellites orbiting the Earth in the same circular orbit. We need to determine what physical quantity they must have in common.

2. **Relevant Formula**: The orbital velocity \( v \) of a satellite in a circular orbit is given by the formula:
\[ v = \sqrt{\frac{GM}{r}} \]
where:
- \( G \) is the gravitational constant,
- \( M \) is the mass of the Earth,
- \( r \) is the radius of the orbit (distance from the center of the Earth to the satellite).

3. **Identifying Constants**: Since both satellites are in the same orbit, they share the same radius \( r \). The mass of the Earth \( M \) and the gravitational constant \( G \) are also constants.

4. **Calculating Velocity**: Since \( G \), \( M \), and \( r \) are the same for both satellites, the orbital velocity \( v \) for both satellites will be the same. Thus, we can conclude:
\[ v_1 = v_2 \]

5. **Conclusion**: Therefore, the two satellites must have the same orbital velocity.

### Final Answer:
The two Earth satellites must have the same **orbital velocity**.

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