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

Q: n small balls each of mass m impinge elastically each second on a surface with velocity u. the force experienced by the surface will be

(a) mnu

(b) 2mnu

(c) 4mnu

(d) (1/2) mnu

Ans: (b)