1. Chapter 12 Section 2 What is a Force?

2. Force A force is a push or a pull. Measured in newtons (N).
All forces have both size and direction.

3. Forces Acting on Objects
A force can change the velocity of an object.
A force can change:
*speed
*direction
*both

4. A Giver and a Receiver are Required
Something must give the push (or pull) and something else has to receive the push (or pull).
Examples:

5. Forces in Combination
The net force is the force that results from combining all the forces exerted on an object.

6. Forces in the Same Direction
Net force = force 1 + force 2
Example: You are pushing a piano with 25 N of force to the right and your friend is pulling the piano with 20 N of force to the right. What is the net force on the piano?
25 N + 20 N = 45 N

7. Forces in Opposite Directions
Net force = force 1 - force 2
Example: In a game of tug-of-war, one dog is pulling with a force of 12 N to the left and the other dog is pulling with a force of 10 N to the right. What is the net force on the rope and in what direction?
12 N - 10 N = 2 N to the left

8. Unbalanced and Balanced Forces
When the net force on an object is greater than zero the forces are unbalanced.

9. When the net force is zero, the forces are balanced.
––––> No movement happens

10. Tension, Compression, and Gravity
Tension is a force that is exerted when matter is pulled or stretched.
Ex. Tension on a dog leash
Compression is a force that is exerted when matter is pushed or squeezed.
Ex. Kittens on a pillow exerting compression upward
Gravity is a force that pulls objects downward

11. LET’S TRY IT!!!!
We’re going to see how forces affect structures.

12. Fettuccine Structures
Guidelines:
No pillars or columns (bundles)
No fences
No piles
No stacking
1 structure- be able to move it as one piece