JEE MAIN - Physics (2019 - 9th April Morning Slot - No. 19)
A solid sphere of mass 'M' and radius 'a' is
surrounded by a uniform concentric spherical
shell of thickness 2a and mass 2M. The
gravitational field at distance '3a' from the
centre will be :
$${{GM} \over {3{a^2}}}$$
$${{2GM} \over {9{a^2}}}$$
$${{GM} \over {9{a^2}}}$$
$${{2GM} \over {3{a^2}}}$$
Explanation
We use Gauss’s Law for gravitation
g.4$$\pi $$r2 = (Mass enclosed) 4$$\pi $$G
$$g = {{3M4\pi G} \over {4\pi {{(3a)}^2}}} = {{GM} \over {3{a^2}}}$$
g.4$$\pi $$r2 = (Mass enclosed) 4$$\pi $$G
$$g = {{3M4\pi G} \over {4\pi {{(3a)}^2}}} = {{GM} \over {3{a^2}}}$$
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