n small balls, each of mass m impinge elastically each second on a surface with a velocity u , then the force experienced by the surface in one second, will be

Step-by-step solution

Force experienced by the surface is equal to change in momentum in one second. From Newton's second law of motion, the rate of change of momentum of a body is equal to the external force applied on the body and the change in momentum always takes place in the direction of the force. Momentum of ball before impact =m u Momentum after impact =-m u Change in momentum =m u-(-m u)=2 m u Change in momentum due to n balls in one second is =2 mnu . Change of momentum = force experienced per second =2 mnu .