1. Unit 5 Reassessment Review - FORCES
Directions: To view this presentation correctly click “Slideshow” then “From Beginning”. There are many animations and helpful examples so read carefully! Take notes when you see the pencil. Use page titles as subheadings to keep your notes organized.

2. Balanced & Unbalanced Forces

3. Force 1000 kg What is force? Push or Pull
It’s what causes “things” to accelerate
1000 kg

4. Net Force
The combination of all forces acting on an object.

5. Adding Forces
5 N
5 N
= 10 N
Two forces in the same direction are added together to produce a net force in that direction.

6. Subtracting Forces 10 N = 5 N 5 N
When forces are in opposite directions you subtract to produce a net force that will move in the direction of the larger force.

7. Balanced Forces
If all forces are balanced there is no acceleration in any direction.
The Net Force is 0N.

8. Balanced Forces (Balanced Forces = No Acceleration)
Object
5 N
5 N
Notice that all the forces are equally pointed in the opposite direction. Hence they balance each other – or cancel each other.
Equal Pushing
Forces may cancel each other and produce a Net Force of 0!

9. Balanced Forces Example (Balanced Forces = No Acceleration)
Ground pushes up
Gravity pulls down
Gravity pulls down on you…
The ground pushes back up…
THIS KEEPS YOU WHERE YOU ARE!
If these football players push
on each other equally as hard,
will either one move?

10. Balanced Forces Example (Balanced Forces = No Acceleration)
Equal Pushing
Equal Pulling
5 N
5 N
Forces may cancel each other and produce No Acceleration!

11. Balanced Forces Balanced Push No Change in Motion i.e. Pushing a Car
Pull
i.e. Tug-o-war
10N
10N
10N
10N

12. Unbalanced Forces
If one force is greater than the opposing force we get acceleration in a direction.
The net force will NOT be equal to 0N.

13. Unbalanced Forces Cause Acceleration
Adding Forces
Subtracting Forces

14. Unbalanced Forces Causes Acceleration
Adding Forces
Object
5 N
5 N
Notice that all the forces are pointed in the same direction. Hence they add together.

15. Unbalanced Forces Causes Acceleration
Subtracting Forces
Object
20 N
5 N
Net Force of 15N to the Right
Notice that the forces are unequal and pointed in the opposite direction. Hence they are unbalanced and in opposition to each other – or one partially cancels the other.

16. Un-Balanced Forces Additive Un-Balanced Same Direction
so you ADD
Moves 20 N to the Right.
Subtractive
Opposite Direction
So you SUBTRACT
Moves 10 N to the right
10N
10N
20N
10N