# A solid sphere of uniform density and radius  applies a gravitational force of attraction equal to on a particle placed at , distance  from the centre  of the sphere. A spherical cavity of radius  is now made in the sphere as shown in figure. The sphere with cavity now applied an gravitational force  on same particle placed at . The ratio  will be a) 1/2 b) 7/ 9 c) 3 d) 7

## Question ID - 55345 | SaraNextGen Top Answer A solid sphere of uniform density and radius  applies a gravitational force of attraction equal to on a particle placed at , distance  from the centre  of the sphere. A spherical cavity of radius  is now made in the sphere as shown in figure. The sphere with cavity now applied an gravitational force  on same particle placed at . The ratio  will be a) 1/2 b) 7/ 9 c) 3 d) 7

Answer Key / Explanation : (b) -

(b)

Gravitational force due to solid sphere,

where  and  are mass of the solid sphere and particle respectively and  is the radius of the sphere. The gravitational force on particle due to sphere with cavity = force due to solid sphere creating cavity, assumed to be present above at that position

So,