Introduction
Recall from our study of the work-energy method on particles that
Method of Work and Energy
Method of Impulse and Momentum
The work-energy method is quite useful when a system of particles forms a rigid body. For example, when two particles are connected by a rigid link, the work done by the internal forces cancel each other out.
Newton's second law is often used with the principle of work and energy, so a complete FBD should be drawn, including forces that do no work.