Question

A point mass $m_0$ is placed at a distance $\frac{R}{3}$ from the centre of a spherical shell of mass M and radius R. The gravitational force on the point mass $m_0$ is

• A. $\frac{9GM{m}_0}{R^2}$
• B. $\frac{GM{m}_0}{R^2}$
• C. $Zero$
• D. $\frac{4GM{m}_0}{R^2}$

Answer 1

The correct option is C $Zero$

If we draw an imaginary sphere of radius $R/3$ around the center $(Gaussian$ surface) then it will not contain any mass because the original sphere is hollow.

So the gravitational field at the surface of this $imaginary$ sphere will be zero so the field at distance $R/3$ from center

will be $zero$.

As field is zero so Force will be also be $Zero$.

Option C is correct.

Note- The gravitational field inside a shell is always $zero$.