A boy standing on a stationary lift (open from above) throws a ball upwards with the maximum initial speed he can, equal to 49 m/s. How much time does the bail take to return to his hands? If the lift starts moving up with a uniform speed of 5 m/s and the boy again throws the ball up with the maximum speed he can, how long does the ball take to return to his hands?

A player throws a bail upwards with an initial speed of 29.4 m s^-1 . To what height does the ball rise and after how long does the ball return to the player’s hands? (Take g = 9.8 m s-2 and. neglect air resistance).

A player throws a bail upwards with an initial speed of 29.4 m s^-1 . Choose the x = 0 m and t = 0 s to be the location and time of the bail at its highest point, vertically downward direction to be the positive direction of x-axis, and give the signs of position, velocity and acceleration of the ball during its upward, and downward motion.

A man can swim with a speed of 4.0 km/h in still water. How long does he take to cross a river 1.0 km wide if the river flows steadily at 3.0 km/h and he makes his strokes normal to the river current? How far down the river does he go when he reaches the other bank?

A monkey of mass 40 kg climbs on a rope (Fig. 5.20) which can stand a maximum tension of 600 N. In which of the following cases will the rope break: the monkey (a) climbs up with an acceleration of 6 m s^2 (b) climbs down with an acceleration of 4 m s^2 (c) climbs up with a uniform speed of 5 m s^1 (d) falls down the rope nearly freely under gravity? (Ignore the mass of the rope).

A cricket ball is vertically thrown up with a velocity 20 m/s. If the acceleration' - in the opposite direction is 10 m//s^2 , how high will the ball rise? What time will it take to reach the maximum height?

(a) A child stands at the centre of a turntable with his two arms outstretched. The turntable is set rotating with an angular speed of 40 rev/min. How much is the angular speed of the child if he folds his hands back and thereby reduces his moment of inertia to 2/5 times the initial value? Assume that the turntable rotates without friction. (b) Show that the child’s new kinetic energy of rotation is more than the initial kinetic energy of rotation. How do you account for this increase in kinetic energy?