State Newton’s second law of motion and derive F = ma. (NCERT Class 9, Force and Laws of Motion – Very Important)

Answer: Newton’s second law: The rate of change of momentum of a body is directly proportional to the applied force and occurs in the direction of force. If a body of mass m changes velocity from u to v in time t, momentum changes from mu to mv. Rate of change of momentum = (mv−mu)/t = m(v−u)/t = ma. Taking proportionality constant as 1 in SI units, F = ma.