A metal sphere of mass '$$m$$' and density '$$\sigma_1$$' falls with terminal velocity through a container containing liquid. The density of liquid is '$$\sigma_2$$'. The viscous force acting on the sphere is

Two uniform wires of same material are vibrating under the same tension. If the first overtone of first wire is equal to the $$2^{\text {nd }}$$ overtone of $$2^{\text {nd }}$$ wire and radius of the first wire is twice the radius of the $$2^{\text {nd }}$$ wire then the ratio of length of first wire to $$2^{\text {nd }}$$ wire is

A body is projected vertically from earth's surface with velocity equal to half the escape velocity. The maximum height reached by the satellite is ( $$R$$ = radius of earth)

A ball of mass '$$\mathrm{m}$$' is dropped from a height '$$\mathrm{s}$$' on a horizontal platform fixed at the top of a vertical spring. The platform is depressed by a distance '$$h$$'. The spring constant is ( $$\mathrm{g}=$$ acceleration due to gravity)