A small ball of mass $$\mathrm{M}$$ and density $$\rho$$ is dropped in a viscous liquid of density $$\rho_{0}$$. After some time, the ball falls with a constant velocity. What is the viscous force on the ball ?

A small block of mass $$100 \mathrm{~g}$$ is tied to a spring of spring constant $$7.5 \mathrm{~N} / \mathrm{m}$$ and length $$20 \mathrm{~cm}$$. The other end of spring is fixed at a particular point A. If the block moves in a circular path on a smooth horizontal surface with constant angular velocity $$5 ~\mathrm{rad} / \mathrm{s}$$ about point $$\mathrm{A}$$, then tension in the spring is -

Given below are two statements : one is labelled as Assertion $$\mathbf{A}$$ and the other is labelled as Reason $$\mathbf{R}$$.

Assertion A : Earth has atmosphere whereas moon doesn't have any atmosphere.

Reason R : The escape velocity on moon is very small as compared to that on earth.

In the light of the above statements, choose the correct answer from the options given below:

The kinetic energy of an electron, $$\alpha$$-particle and a proton are given as $$4 \mathrm{~K}, 2 \mathrm{~K}$$ and $$\mathrm{K}$$ respectively. The de-Broglie wavelength associated with electron $$(\lambda \mathrm{e}), \alpha$$-particle $$((\lambda \alpha)$$ and the proton $$(\lambda p)$$ are as follows: