1. Introduction to Forces & Free Body Diagramming
MIT C.P. PHYSICS
Introduction to Forces & Free Body Diagramming

2. Support force exerted by a surface
Types of Forces
Gravity
F(g)
Weight
Friction
F(f)
Static & Sliding
Applied Force
F(app)
Force applied by a person or object
Normal Force
F(n)
Support force exerted by a surface
In the fifth century B.C., Democritus hypothesized that all matter is composed of tiny indestructible units, called atoms.
Air Resistance
F(air)
Drag
Tension
F(tens)
Forces pulling on opposite ends
Spring
F(spring)
Compression or tension

3. What Is Free Body Diagramming?

4. Free Body Diagrams
A Free Body Diagram is a simple diagram that shows the size and direction of all the forces acting on a body!

7. Free Body Diagrams

8. Problem Strategy Determine all the forces acting on the body.
2. Determine the direction of each force.
3. Draw the object as a BOX or a POINT.
4. Draw each force connected to the object as a vector.

9. Sample Problem A teacher sits at his desk.
1. Determine all the forces acting on the body.
Gravity & Normal Force
2. Determine the direction of each force.
Gravity ↓ Normal Force ↑

10. Sample Problem A teacher sits at his desk.
3. Draw the object as a BOX or a POINT.
4. Draw each force connected to the object as a vector .
Since the teacher isn’t moving, both vectors should be the same size!

11. Sample Problem
A book slides across a table top with constant velocity.
Constant velocity means all the forces must balance each other out.
An accelerating book slides across a table top.
Since the book is accelerating, the applied force must be larger than the friction force.

12. Lab: Free Body Diagramming?

13. Lab: Free Body Diagramming?
Data Chart
Situation
Diagram 1 2 3 4 5 6 7 8 9 10 11 12