A slab of stone of area 0.36 m² and thickness 0.1 m is exposed on the lower surface to steam at 100^oC. A block of ice at 0^oC rests on the upper surface of the slab. In one hour 4.8 kg of ice is melted. The thermal conductivity of slab is
(Given latent heat of fusion of ice = 3.36 $$ \times $$ 10⁵ J kg^$$-$$1)

Which one of the following plots represents the variation of gravitiational field on a particle with distance r due to a thin spherical shell of radius R? (r is measured from the centre of the spherical shell)

If $${v_e}$$ is escape velocity and $${v_o}$$ is orbital velocity of a satellite for orbit close to the earth's surface, then these are related by

A circular platform is mounted on a frictionless vertical axle. Its radius R = 2 m and its moment of inertia about the axle is 200 kg m². It is initially at rest. A 50 kg man stands on the edge of the platform and begins to walk along the edge at the speed of 1 ms^$$-$$1 relative to the ground. Time taken by the man to complete one revolution is