For a transistor, the current ratio $$\alpha_{\mathrm{dc}}=\frac{69}{70}$$, the current gain $$\beta_{\mathrm{dc}}$$ is

'n' small drops of same size fall through air with constant velocity $$5 \mathrm{~cm} / \mathrm{s}$$. They coalesce to form a big drop. The terminal velocity of the big drop is

The depth from the surface of the earth of radius $$\mathrm{R}$$, at which acceleration due to gravity will be $$60 \%$$ of the value on the earth surface is

A body of mass 'm' is moving with speed 'V' along a circular path of radius 'r'. Now the speed is reduced to $$\frac{V}{2}$$ and radius is increased to '3r'. For this change, initial centripetal force needs to be