A boat moves with a speed of $5 \,km/h $ relative to water in a river flowing with a speed of $3 \,km/h$ and having a width of $1 \,km$. The minimum time taken around a round trip is.........$min$

The rebound coefficient between a tennis ball and a racket is defined as $g = v_2/ v_1$, where $v_1$ is the incoming speed of the ball and $v_2$ is the speed of the ball after rebound while the racket is at rest. A tennis ball falls from height $H$ to a racket at rest and bounces back to $0.8\  H. A$ tennis player is using the racket to hit an incoming tennis ball traveling at $150\ km/hr$ and the racket is moving at $100\ km/hr$. What is the speed of the ball after being hit? (Assume the mass of the racket >> that of the ball)..........$km/hr$

A particle $(A)$ moves due north at $3\,km / h$ another particle $(B)$ due west at $4\,km / h$. The relative velocity of $A$ with respect to $B$ is $\left(\tan 37^{\circ}=3 / 4\right)$

A man is crossing a river flowing with velocity of $5\, m/s$. He reaches a point directly across at a distance of $60\, m$ in $5\, sec$. His velocity in still water should be........$m/s$

Ram moves in east direction at a speed of $6 \,m / s$ and Shyam moves $30^{\circ}$ east of north at a speed of $6 \,m / s$. The magnitude of their relative velocity is ........ $m / s$

The speed of a swimmer is $4\,km\,h ^{-1}$ in still water. If the swimmer makes his strokes normal to the flow of river of width $1\,km$, he reaches a point $750 \,m$ down the stream on the opposite bank.The speed of the river water is $.........km h ^{-1}$