2. Motion and Force

3. Chapter Thirteen: Forces
13.2 Forces and Equilibrium

4. Same direction different magnitude
13.2 Vectors
Force is a vector.
Vectors have information about both direction and magnitude (size of the force)
Same direction different magnitude
Medium Force
Small Force
Large Force

5. 13.2 Adding forces
The sum of all the forces on an object is called the net force.
The net force will have both direction and magnitude.
To figure out if or how an object will move, we look at ALL of the forces acting on it.

6. 4.3 Adding forces
In what direction will this plane move?

7. 13.2 Normal forces
When the net force on an object is zero, we say the object is in equilibrium.
This means that the forces are balanced.

8. 13.2 Equilibrium and normal forces
A normal force is created whenever an object is in contact with a surface.
The normal force is equal in magnitude to the force pressing the object into the surface, which is often the object’s weight.
The normal force is sometimes called the support force.

9. 13.2 The free body diagram
How do you keep track of many forces with different directions?
Draw a free-body diagram that contains the objects, like a book on a table.

11. 13.2 Solving equilibrium problems
For an object to be in equilibrium, all the forces acting on the object must add up to zero.
Is this object in equilibrium?

12. Technology Connection
Defy Gravity? It Can Be Done.
When the force of lift is stronger than the force of an airplane’s weight, it will leave the ground and fly. How do we create the force of lift?