A simple pendulum is suspended from the ceiling of an empty box falling in air
near earth surface. The total mass of system is \(M\). The box experiences air
resistance \(\vec{R}=-k \vec{v}\), where \(v\) is the velocity of box and \(k\) is a
positive constant. After some time, it is found that period of oscillation of
pendulum becomes double the value when it would have suspended from a point on
earth. The velocity of box at that moment \(v=\frac{M g}{n k}\), then the value
of \(\mathrm{n}\) is. (Take \(g\) in air same as on earth's surface.)