A ball of mass 300 g is dropped from a height 10 m above a sandy ground. On reaching the ground, it penetrates through a distance 1 . 5 m in sand and finally stops. The average resistance offered by the sand to oppose the motion is (acceleration due to gravity = 10 m s - 2 )

Step-by-step solution

Net displacement of the ball under the action of gravity is 10 + 1 . 5   m . According to work energy theorem, work done by all the forces on a sytem is equal to the change in kinetic energy of the system. Therefore, W g + W R = 0 ⇒ m g h + d - F R d = 0 ⇒ 0 . 3 × 10 × 11 . 5 - F R × 1 . 5 = 0 ⇒ F R = 23   N