Within a spherical charge distribution of charge density $$\rho $$(r), N equipotential surfaces of potential V₀, V₀ + $$\Delta $$V, V₀ + 2$$\Delta $$V, .......... V₀ + N$$\Delta $$V ($$\Delta $$ V > 0), are drawn and have increasing radii r₀, r₁, r₂,..........r_N, respectively. If the difference in the radii of the surfaces is constant for all values of V₀ and $$\Delta $$V then :

In an engine the piston undergoes vertical simple harmonic motion with amplitude 7 cm. A washer rests on top of the piston and moves with it. The motor speed is slowly increased. The frequency of the piston at which the washer no longer stays in contact with the piston, is close to :

The resistance of an electrical toaster has a temperature dependence given by R(T) = R₀ [1 + $$\alpha $$(T − T₀)] in its range of operation. At T₀ = 300 K, R = 100 $$\Omega $$ and at T = 500 K, R = 120 $$\Omega $$. The toaster is connected to a voltage source at 200 V and its temperature is raised at a constant rate from 300 to 500 K in 30 s. The total work done in raising the temperature is :

An astronaut of mass m is working on a satellite orbiting the earth at a distance h from the earth’s surface. The radius of the earth is R, while its mass is M. The gravitational pull F_G on the astronaut is :