1. Warm Up
A block of aluminum occupies a volume of 15.0 mL and has a mass of 40.5 g.
What is its density?

2. Which wrestler is going to win and why?

3. Force

4. FORCE
A FORCE is a push or pull!

5. Two different types of forces.
Balanced Forces
Unbalanced Forces

6. UNBALANCED FORCES
UNBALANCED FORCES occur when two forces act on each other, but one is stronger.
Unbalanced Forces
A change in movement or direction occurs!

7. BALANCED FORCES
BALANCED FORCES occur when two forces act on an object with the same amount of force.
No change in speed or direction

8. Net Force
Usually more than one force is acting on an object at the same time.
Sometimes these forces are applied in the same direction, and sometimes they are applied in different directions.

9. Net Force
Net Force – the net force is the combination of all forces acting on the object.

10. Example 1: 1500 N 1500 N Is this force a push or pull?
Are the forces working together or opposite of each other?
Are the forces equal or not equal?
Are the forces balanced?
What is the net force?
Is there a change in motion?
Yes No

11. Example 2: 700 N 500 N Are the forces equal or not equal?
Are the forces balanced?
Is the stronger force pulling to the right or left?
Is there a change in motion?
What is the net force?
In what direction? No
Left
Yes
= 200N
Left

12. Are the forces working together or opposite? What is the net force?
Example 3:
700 N
500 N
It was your turn to fill the tank!
I filled it
last!
Are the forces working together or opposite?
What is the net force?
In what direction?
1200 N
Forward, left

13. Example 4:
Net Force
When the forces are acting in the SAME DIRECTION, the forces are ADDED.
30 N to the right
30 N to right
+ 25 N to right
55 N to right
25 N to the right

14. Example 5:
Net Force
When the forces are acting in the OPPOSITE DIRECTION, the forces are SUBTRACTED.
30 N to right
- 25 N to LEFT
5 N to right
25 N to the LEFT
30 N to the right

15. In the same direction = ADD
In the opposite direction= SUBTRACT OR OR

16. STAAR
Marcelo and Jesus are playing tug of war. Marcelo is pulling left on one end of a rope with 10N of force, while Jesus is pulling on the other end of the same rope with 12N of force. Who’s pulling harder? How many Newtons harder is he pulling it?
A Jesus, 12N Harder
B Jesus, 2N Harder
C Marcelo, 10N Harder
D Marcelo, 2N Harder

17. STAAR
50 N
Use the diagram to answer the following question. The arrows below show forces acting on an object.
What is the net force on the object and in what direction would the object move?
A. 100 N to the right
B. 100 N to the left
C. 100 N upward
D. 150 N upward
100 N
100 N
150 N

18. A ball is rolling across a field with a force of 20 N
A ball is rolling across a field with a force of 20 N. If the force of friction from the field is 3.7 N, what would be the net force of the ball?

19. Jose kicked a soccer ball with a force of 20 N toward the goal
Jose kicked a soccer ball with a force of 20 N toward the goal. The goalie dove and caused the ball to bounce away from the goal. The goalie was able to change the direction the ball because:
A. He exerted a force on the ball equal to
0 N.
B. He exerted a force on the ball less than
20 N.
C. He exerted a force on the ball greater than 20 N.
D. He exerted a force on the ball equal to