Q15 of 21 Page 109

A stone of mass 5kg falls from the top of a cliff 50m high and buries 1m in deep in sand. Find average resistance offered by sand.

Mass of stone = M = 5 kg

Height of the cliff = h = 50 m


Case I: before hitting the ground


Since the stone falls freely, a = g = 9.8 ms–2


Stone falls from rest, initial speed = u = 0


s = h = 50 m





v = speed of stone before hitting the ground


Case II: After hitting the ground when stone penetrates the sand


Final speed = v = 0


Initial speed = u


Distance travelled in sand = s = 1 m





Negative sign indicates that it is retardation




Negative sign indicates that its a resistive force


Average resistive force offered by the sand =


More from this chapter

All 21 →
13

A man of mass 50 kg carries a bag of weight 40N on his shoulder. The force with which the floor pushes up his feet will be?

 14

Two blocks A and B of masses 5kg and 3kg respectively rest on a smooth horizontal surface with B over A. The co-efficient of friction between A and B is 0.5 .The maximum horizontal force that can be applied to A so that there will be motion of A and B without relative slipping is?

 16

An object with a mass 10kg moves at constant velocity of 10ms–1. A constant force then acts for 4 s on the object and gives it a speed of 2 ms–1 in opposite direction. What is the acceleration produced?

 17

When you kick a stone you get hurt. Due to which property does this happen?