Question

what is second law of motion

Answer 1

According to newton's second law of motion the rate of change of linear momentum is directly to the external force applied on the body .Now rate of change of linear momentum can be obtain by dividing change in linear momentum of a body by time taken .Then according to newtons second law of motion change in linear momentum

Answer 2

NEWTON'S 2nd law of motion states that the rate of change in momentum of a body is directly proportional to the force applied on that object. And in the direction of applied force, momentum takes place.
F = dp/dt
   = d(mv)/dt
   = m dv/dt
   F = ma