Question

According to Newton's law of gravitation, the magnitude of the force $F$ on point masses $m_1$ and $m_2$ (say) is given by $|F|=\frac{G{m}_1{m}_2}{r^2}$.
I. This equation is not directly applicable for the gravitational force between extended object (like the earth) and a point mass.
II. This equation can be directly applied for gravitational force between an extended object and a point mass.
III. The equations can be applied to find the gravitational force between an extended object and a point mass provided $r$ is the distance of the point mass from the geometric centre of the extended object.
IV. None of the above
Which of the following statement(s) about this equation is/are correct?

• A. Only I
• B. Both I and II
• C. Both II and IV
• D. Both II and III

Answer 1

Answer: (A)

For the gravitational force between an extended object (like the earth) and a point mass, the Newton's universal law of gravitation is not directly applicable. So, statement I is correct but II and III are incorrect.