Question

n balls each of mass m impinge elastically in each second on a surface with velocity u. the average force experienced by the surface with be?

Answer 1

Force = rate of change in momentum

Force = mdv/dt

Force = n*m(v2 - v1)/t

Force = n*m(u - (-u))/t
Final velocity is in opposite direction of initial velocity.

Force = 2nmu/t

According to question t = 1

Force = 2nmu