16.A body of mass 10 kg is to be raised by a massless string from rest to rest, through a height 9.8 m. The greatest tension which the string can safely bear is 20 kg wt. The least time of ascent is:

17.A particle is acted upon by a force of constant magnitude which is always perpendicular to the velocity of the particle. The motion of the particle takes place in a plane. It follows that:

18.An empty plastic box of mass 5 kg is observed to accelerate up at the rate of g / 6 when placed deep inside water. What mass of sand should be put inside the box so that it may accelerate down at the rate of g / 6?

19.Steady rain, giving 5 m m an hour, turns suddenly into a downpour giving 20 mm an hour and the speed of the rain drops falling vertically on to a flat foof simultaneously doubles. The pressure exerted by the falling rain on the roof is raised by a factor of

20.An elevator and its load have a total mass of 800 kg. The elevator is originally moving downwards at 10 m/s, it slows down to stop with constant acceleration in a distance of 25 m. Find the tension T in the supporting cable while the elevator is being brought to rest. (Take g = 10 m/square second)