2. Force: push or pull  all forces have size and direction  measured in Newtons (N) An object will speed up, slow down, or turn Only if something is pushing or pulling on it.

3. Usually, more than one force is acting on an object.  Net Force: Combination of all forces on an object  Determines motion of object (similar to total velocity)

4. When forces act in the same direction, you add the forces to determine the net force. The net force will be in the same direction as the individual forces. 25 N20 N Net Force 25 N + 20 N = 45 N to the right

5. When two forces act in opposite directions,subtract the smaller force from the larger force. The net force will be in the same direction as the larger force. 35 N 20 N Net Force 35 N – 20 N = 15 N Up

6. This is ZERO fun!!! 12 N

7. Eat it!!! Don’t wipe that on me! 12 N 20 N

9. What force was missing in the video? Friction: slows motion, can cause moving objects to slow down and stop

10. Force Between Surfaces Surface Roughness Source of Friction As force increases, friction increases. The rougher the surface is, the greater the friction is.

11. Kinetic Friction: “moving”, friction between moving surfaces Rolling and Sliding Friction Unbalanced Force—Net Force Doesn’t = Zero Static Friction: “not moving” Balanced Force—Net Force = ZERO