Question

Two stones lying on the surface of the Earth have mass, a gravitational force will always exist between them and it will try to pull the stones towards each other. But actually, we don’t see the stones moving towards each other, why?

Statement 1: The gravitational force is very less.

Statement 2: Stones are lying on a flat surface, so they cannot move.

Statement 3: The gravitational force is very less to overcome friction.

Statement 4: The stones are irregular in shape, so they cannot move.

Which statements explains the reason for the above question?

• A. Statement 1 and 2 are the reasons
• B. Statement 1 and 3 are the reasons
• C. Only statement 4 is the reason
• D. Statement 3 and 4 are the reasons

Answer 1

The correct option is B

Statement 1 and 3 are the reasons

Let’s take an example to understand the question:
Let us consider the mass of each stone as 5 kg. They are separated by a distance of 1 m.
F = $\frac{GmM}{r^2}$
F = $\frac{6.67\times {10}^{-11}\times 5\times 5}{1}$= $66.7\times {10}^{-11}$ N
Thus, statement 1 is correct. Also, force of gravitation (only in the range of ${10}^{-12}$ N) between them is much lower to overcome the frictional force (in the order of tens of newtons). Therefore, they do not move. Thus, statement 3 is also correct.