Application of Newton's Laws

Having stated the three laws, this section develops the standard toolkit for applying them to real mechanical systems: drawing a free body diagram, analysing motion on an inclined plane, analysing blocks in direct contact, analysing bodies connected by strings over a pulley, and resolving concurrent forces via Lami's theorem.

Before applying Newton's laws to any problem, four steps are always followed:

1. Choose a suitable inertial coordinate system (Earth is usually adequate).
2. Clearly identify the system — a single object, or a group of objects — to which the laws are being applied.
3. Draw the free body diagram for that system. …