A body of mass $$10 \mathrm{~kg}$$ is kept on a horizontal surface. The coefficient of kinetic friction between the body and the surface is 0.5. A horizontal force of $$60 \mathrm{~N}$$ is applied on the body. The resulting acceleration of the body is about
A ball of mass $$0.2 \mathrm{~kg}$$ is thrown vertically down from a height of $$10 \mathrm{~m}$$. It collides with the floor and loses $$50 \%$$ of its energy and then rises back to the same height. The value of its initial velocity is
The moment of inertia of a rigid body about an axis
Seven identical discs are arranged in a planar pattern, so as to touch each other as shown in the figure. Each disc has mass $$m$$ radius $$R$$. What is the moment of inertia of system of six discs about an axis passing through the centre of central disc and normal to plane of all discs?