Question

$\text{Assertion}:$ 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 $\frac{G{m}_1{m}_2}{r^2}$

$\text{Reason}:$ According to Newton's law of gravitation, gravitational force between two point masses $m_1$ and $m_2$ separated by a distance $r$ is $\frac{G{m}_1{m}_2}{r^2}$

• A. Both assertion and reason are true and reason is the correct explanation of assertion.
• B. Both assertion and reason are true, but reason is not the correct explanation of assertion.
• C. Assertion is true, but reason is false.
• D. Assertion is false, but reason is true.

Answer 1

The correct option is D Assertion is false, but reason is true.

According to Newton's law of gravitation,

$F=G\frac{m_1{m}_2}{r^2}$

This universal law of gravitation is valid only for point masses.

So, option $\left(d\right)$ is correct.

Why this question ? To make students understand the limitation of the universal law of gravitation. Tip: For uniform spherical masses, gravitational force can be calculated assuming them to be point masses placed at their centers.