1. Ch. 12 Sec. 1 Forces

2. What is a Force?  Causes an object to move, or accelerate by causing a speed or direction change  Unit = Newton (N) Force that causes 1 kg mass to accelerate a 1 m/s 2 Force represented by arrows (vector quantity) Forces in the same direction combines by addition. Forces in the opposite direction combines by subtraction

3. Types Balanced Forces  No change in motion. Opposite in direction and equal in size.  Net force = 0 Unbalanced Forces  One force is greater. “Net” force on an object is one direction. OR

4. Acting on objects  Always draw arrows around an object Plane?

5. Friction  Force that opposes motion.  depends upon weight, texture, & surface area  Four Types

6. Friction  Static Force that acts on objects that aren’t moving  Sliding Opposes the direction of motion as object slides

7. Friction  Rolling Force that acts on rolling objects  Fluid Opposes motion through a liquid

8.  Ways to Reduce? ~ Lubricants – oil, grease, WD- 40. Used in devices that have moving parts. Ex. engines  Helpful? ~ Motion ~ keep from slipping & sliding Friction

9. Gravity force of attraction between objects Newton’s Law of Universal Gravitation ~All objects in the universe attract each other by the force of gravity. ~ depends on the mass of objects & the distance between them.

10. Gravity: Falling Objects  Gravity accelerates an object downward Accelerates at 9.8 m/s/s  Balanced upward force  Terminal Velocity Constant velocity of a falling object

11. Projectile Motion  Projectile Motion Curved path of a falling object Falls at same rate as a falling object