1. Free-Body Diagrams
Understanding forces

2. Definition
A free-body diagram is a simple diagram that shows the size and direction of all the forces acting on an object

3. FNormal FApplied FFriction FGravity Example p
1.) Force Applied (The dog running forward)
2.) Force of Friction (Dogs paws hitting the ground)
3.) Force of Gravity (Weight of the dog on the ground)
4.) Normal Force (The ground applying equal but opposite force upward)
FGravity

4. Force causing the object to move Opposite the force of friction
Force Applied
Force causing the object to move
Opposite the force of friction
Force of Friction
Force causing the object to slow down
Opposite the force applied
Force of Gravity
The weight of the object on the ground
Opposite the normal force
Normal Force
Force applied to the object from the ground
Opposite the force of gravity

5. Strategies for Constructing a Free-Body Diagram
Read the Problem
Determine all the forces that are acting on the object
Determine the direction that each force is acting

6. Steps for Constructing a Free-Body Diagram
Draw the object as a box
Draw each force as an arrow
Attach each arrow to the box
Aim the tip of each arrow in the direction the force is acting
Label each arrow

7. Lets Try Some Examples
A radio sits on a bookshelf. Observe the forces acting on the radio

8. Example 1 Remember Read the Problem
Determine all the forces that are acting on the object
Determine the direction that each force is acting

9. Example 1 The force of gravity acts on the radio
Remember
The force of gravity acts on the radio
The direction is downward
The force of the bookshelf holds up the radio
The direction is upward

10. FNormal FGravity The Free-Body Diagram
The Free-Body Diagram will look like this
FNormal
FGravity

11. Example 2
A car traveling down a road. Observe the forces acting on the car.

12. Example 2 The force of gravity acts on the car downward
The force of the road holds the car upward
The force of the engine moves the car forward
The Friction against the wheels and the road pull backwards
No Force of Friction or Applied force because it is not moving

13. FNormal FFriction FEngine FGravity The Free-Body Diagram
The Free-Body Diagram will look like this
FNormal
FFriction
FEngine
The Force of Friction is Less Than the Force of the engine because it is moving forward
FGravity

14. For You To Do
Finish the worksheet in groups. Remember the strategies and steps for constructing a free- body diagram