1. Bell ringer- What forces are acting on you right now?

2. What did you learn yesterday?

3. What does it mean to have balanced forces?
What is a net force?
The sum of all forces on an object. (net= total)
What does it mean to have balanced forces?
The net force is zero. When forces are unbalanced object accelerate.
What is a normal force?
The force that a surface exerts on a object that is pressing on it. (normal =perpendicular)
What is a free body diagram?
A diagram showing all the forces acting on an object.

4. What happens when forces are not balanced?
Notes ready!

5. Unbalanced Forces
When two forces acting on an object are not equal in size, we say that they are unbalanced forces.
If the forces on an object are unbalanced this is what happens:
an object that is not moving starts to move
an object that is moving changes speed or direction

6. Net Forces
The size of the overall force acting on an object is called the resultant force or net force. If the forces are balanced, this is zero. In the example above, the net force is the difference between the two forces, which is = 40 N.

7. Practice Problems
Two people are pushing a disabled car. One exerts a force of 200 N east, the other a force of 150 N east. What is the net force exerted on the car? (Assume friction to be negligible.)
Two soccer players kick a ball simultaneously from opposite sides. Red #3 kicks with 50 N of force while Blue #5 kicks with 63 N of force. What is the net force on the ball?

8. When forces act together you ADD them up to find a NET Force.
You will know when two forces are acting together when you see the arrows facing the same direction.
When forces act together you ADD them up to find a NET Force.
Since both of these forces are pointing in the same direction (right), we will add them for a net force of what?
5 Newtons to the right
8 Newtons to the right

9. What direction would the net force go in?
You will know two forces are working AGAINST each other when you see the arrows point in OPPOSITE directions.
When forces are against each other, you SUBTRACT them
What would the
net force be?
What direction would the net force go in?
12 Newtons to the Left
3 Newtons to the right

10. You can tell the direction of a net force by looking at the arrows
If the forces are working together the net force is in the direction of BOTH arrows.
Since both of these arrows are in the same direction, the net force would be to the RIGHT

11. If the forces are working AGAINST each other the net force would be in the direction of the BIGGER arrow.
40 Newtons going right
5 Newtons going left
The DIRECTION of the force will be in the direction of the bigger arrow.
Is the bigger arrow pointing left or right?

12. Example of Unbalanced Forces
Friction holds the tractor in place with a force of 7 Newtons. If the tractor pushes to the left with a force of 65 Newtons, What is the net force? In what direction is the net force going?
ANSWER = 58 Newtons to the LEFT

13. 10 Newtons Right
If the truck on the left pushes RIGHT with a force of 10 Newtons, and the truck on the right pushes LEFT with a force of 10 Newtons, what do you think will happen?

14. Practice worksheet Done early
Go on weebly and do the forces and motion balanced and unbalanced link fill out the lab worksheet