1. Free body diagrams

2. Free Body Diagram Construction
Rules
Draw an arrow representing the weight of the object.
Label the arrow Fg.
3. Draw additional arrows in the appropriate directions to represent any forces acting on the object. The length of the arrows should be proportional to the quantity of the force.

3. Free Body Diagram Construction
Rules
4. Label arrows with appropriate names, e.g.:
Force of Gravity, Fg
Tension, FT (like from a rope)
Normal, FN
Friction, Ff (resistive force caused by sliding surfaces)
Remember, ONLY the arrows constitute the free body diagram.

4. Free Body Diagram Construction
Example
Consider a book sitting on a table, draw a box representing the book but do not draw the table
Draw an arrow representing the weight of the object.
Label the arrow Fg. (Force due to gravity)
Fg=mg

5. 3. Draw additional arrows in the appropriate directions to represent any forces acting on the object. The length of the arrows should be proportional to the quantity of the force.
If there are no forces acting in the horizontal direction, like pushing or pulling the book, then draw no arrows. Here you see the Normal Force, which is the force opposite the contact surface. It is equal and opposite the weight as long as the book is not moving. FN Fg