Newton’s 2nd Law: Fnet = ma
- Force of GravityFg = mg = weight
- Weight is defined as the force of gravity on an object.
- An object’s mass (its inertia) never changes. Its weight depends on the acceleration of gravity.
- Free body diagrams:
- Draw only the object and the forces acting on it.
- Do not draw in velocity, acceleration…
- Once the free body diagram is drawn, write an equation using Fnet = ma.
- Example: A 20 kg cart is pulled forward by a force of 45 Newtons. There is a force of friction of 15 Newtons acting on the object.
Free body diagrams can become much more complicated, but the basic procedure is the same.
- Draw FBD
- Write and Fnet equation and solve.