1. Section 2-1:
What is a force?

2. Forces acting on objects
Force is simply a push or pull on an object
It has both size (a number) and direction
Express force in a unit called a Newton (N)

3. Acting on objects All forces act on objects
Does not mean that motion will occur
Sources and receivers of forces
You cannot see all sources and receivers of forces:
For example:
Magnet’s force on a refrigerator
Air held near Earth by gravity

4. Determining net force
Net force = the combination of all forces acting on an object
Usually there is more than one force acting on an object

5. Forces in the same direction
When forces act in the same direction, you add the forces to determine net force
Mrs. Bannon
20 Newtons Net force =
Mr. Mager Newtons
10 Newtons

6. Forces in opposite directions
When forces act in opposite directions, you subtract the forces to find net force
Net force acts in the direction of the larger force
20 newtons east
10 newtons west
Net force = 10 newtons east

7. Balanced forces
When forces acting on an object produce a net force of o newtons
Will NOT cause a change in motion
10 newtons east
10 newtons west

8. Unbalanced forces
When forces acting on an object produce a net force that is not 0 newtons
20 newtons east
10 newtons west
What is the net force?

9. Unbalanced forces continued
Will cause a change in motion
An object can continue to move, even after the unbalanced forces are removed from the object

10. Forces practice- Push or a pull1. 2. 3. 4. 5.

11. Forces practice 1 Look at the following picture.
Choose the best answer to complete each sentence and write the answer on your board (You do NOT have to write the entire sentence).

12. Practice 1 The forces shown are PUSHING/ PULLING
The forces shown are WORKING TOGETHER/ OPPOSITE FORCES
The forces are EQUAL/ NOT EQUAL
The forces DO/ DO NOT balance each other
The resultant force is 1000N TO THE RIGHT/ 1000 N TO THE LEFT/ ZERO
There IS/ IS NO motion.

13. Forces practice 2 Look at the following picture.
Choose the best answer to complete each sentence and write the answer on your board (You do NOT have to write the entire sentence).

14. Practice 2 The forces shown are PUSHING/ PULLING
The forces shown are WORKING TOGETHER/ OPPOSITE FORCES
The forces are EQUAL/ NOT EQUAL
The forces DO/ DO NOT balance each other
The stronger force is pulling to the RIGHT/ LEFT
The weaker force is pulling to the RIGHT/ LEFT
Motion is to the RIGHT / LEFT