**Newton’s 2 ^{nd} Law: **F

_{net}= ma

**Applications: **

**Force of Gravity**F_{g}= 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 F
_{net}= 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.

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