The mass of moon 1% of mass of earth. The ratio of gravitational pull of earth on moon and that of moon on earth will be

Options

A. `1:1`
B. `1:10`
C. `1:100`
D. `1:1`

Explanation

To solve the problem, we need to find the ratio of the gravitational pull of the Earth on the Moon and that of the Moon on the Earth. We can use Newton's law of universal gravitation for this.

### Step-by-Step Solution:

1. **Define the Masses**:
- Let \( M \) be the mass of the Earth.
- Let \( m \) be the mass of the Moon. According to the problem, \( m = 0.01M \) (since the mass of the Moon is 1% of the mass of the Earth).

2. **Write the Gravitational Force Formula**:
- The gravitational force exerted by the Earth on the Moon (\( F_{E} \)) is given by:
\[ F_{E} = \frac{G M m}{r^2} \]
- The gravitational force exerted by the Moon on the Earth (\( F_{M} \)) is given by:
\[ F_{M} = \frac{G m M}{r^2} \]

3. **Calculate the Forces**:
- Since both expressions for \( F_{E} \) and \( F_{M} \) are identical, we can see that:
\[ F_{E} = F_{M} \]

4. **Find the Ratio**:
- The ratio of the gravitational pull of the Earth on the Moon to that of the Moon on the Earth is:
\[ \frac{F_{E}}{F_{M}} = \frac{F_{E}}{F_{E}} = 1 \]

5. **Conclusion**:
- Therefore, the ratio of the gravitational pull of the Earth on the Moon to that of the Moon on the Earth is \( 1:1 \).

### Final Answer:
The ratio of the gravitational pull of Earth on Moon and that of Moon on Earth is \( 1:1 \).