Assertion : The centres of two cubes of masses `m_(1) and m_(2)` are separated by a distance r. The gravitational force between these two cubes will be `(Gm_(1)m_(2))/(r^(2))`
Reason : According to Newton's law of gravitation, gravitational force between two point masses `m_(1) and m_(2)` separated by a distance r is `(Gm_(1)m_(2))/(r^(2))`.

Options

A. If both Assertin and Reason are correct and Reason is the correct explanation of Assertion
B. If both Assertion and Reason are correct but Reason is not the correct explanation of Assertion
C. If Assertion is true but Reason is false
D. If Assertion is false but Reason is true

Answer

To solve the assertion and reason question, we need to analyze both the assertion and the reason carefully.

### Step-by-Step Solution:

1. **Understanding the Assertion**:
The assertion states that the gravitational force between two cubes of masses \( m_1 \) and \( m_2 \), with their centers separated by a distance \( r \), can be expressed as:
\[ F = \frac{G m_1 m_2}{r^2} \]
Here, \( G \) is the gravitational constant.

2. **Understanding the Reason**:
The reason provided states that according to Newton's law of gravitation, the gravitational force between two point masses \( m_1 \) and \( m_2 \) separated by a distance \( r \) is given by the same formula:
\[ F = \frac{G m_1 m_2}{r^2} \]
This is a well-established law in physics.

3. **Analyzing the Validity of the Reason**:
The reason is indeed correct because it accurately describes Newton's law of gravitation for point masses.

4. **Analyzing the Validity of the Assertion**:
However, the assertion is misleading. The law of gravitation applies to point masses, and while it can be approximated for symmetrical objects like spheres, it does not hold true for cubes or irregular shapes without additional considerations. The gravitational force between two cubes cannot be simplified to the point mass formula because the distribution of mass and the distances between different parts of the cubes vary.

5. **Conclusion**:
Therefore, the assertion is false while the reason is true. This means that the gravitational force between two cubes cannot be accurately described by the formula given in the assertion.

### Final Answer:
- Assertion: False
- Reason: True