- When a body experiences a net force Fnet, its momentum p = mv changes.
- The rate of change of momentum is directly proportional to Fnet.
- If SI units are used,
- For a body with constant mass m, the second law is reduced to Fnet = ma.
- For a body with “changing” mass but “constant” v, the second law is reduced to Fnet = vdm/dt
- Integrating both sides of the equation leads to the concept of impulse.