Free Body Diagrams

A simplified way to draw an object and all the forces that are acting

on it

3 Simple Steps1. Replace the object with a dot.2. Identify all the long-range forces acting

on the object.• We have only discussed one long-range

force – gravity

3. Identify all the contact forces acting on the object.

• Remember that only something that is physically touching the object can apply a contact force

• Possible types of contact forces – push, tension, normal, and friction

Things to Remember

• Always follow all 3 steps• Force due to gravity acts on all objects

and always points down• Force arrows must originate from the dot,

this means that you will never have an arrow pointing at the dot, always away from the dot

• Surfaces apply a normal force that is always perpendicular to the surface (they can be at strange angles-IT IS OKAY)