1. May the Force of Motion Be With You….. October 8, 2009

2. What is a Force…………..  A force is a push or a pull against an object.  Net force = all the combined forces acting on the object  Forces can either be classified as….  Unbalanced – Produces a change in motion – either stopping or starting the motion. (Ex. Ball moving across the grass.) Net force not equal to zero  Balanced – Object not in motion. (EX. Book sitting on a desk.) Net force = to zero  OBJECTS ALSO IN CONSTANT MOTION

3. GRAVITY- THE FORCE OF ATTRACTION FORCE OF ATTRACTION BETWEEN OBJECTS DUE TO THEIR MASSES ALL OBJECTS EXPERIENCE GRAVITY AS ALL OBJECTS HAVE MASS AS MASS INCREASES SO DOES THE GRAVITATIONAL FORCE OF AN OBJECT GRAVITATIONAL FORCE DECREASES AS DISTANCE INCREASES – NEWTON’S LAW OF UNIVERSAL GRAVITATION

4. WEIGHT VS MASS WEIGHT IS THE MEASURE OF GRAVITATIONAL FORCE GIVEN ON AN OBJECT. Due to the Earth’s gravitational force on an object. Measured in Newtons using a spring scale – An object with a 100 g mass will have a weight of 1 newton. MASS IS THE AMOUNT OF MATTER IN AN OBJECT DOES NOT CHANGE DUE TO THE GRAVITATIONAL FORCE ON THE OBJECT – A MAN WITH AN 80 KG MASS ON EARTH WILL HAVE AN 80 KG MASS ON JUPITER. – SAME MAN WITH A WEIGHT OF 131 N WILL HAVE A WEIGHT OF 784 N ON JUPITER

5. MASS VS WEIGHT GRAVITATIONAL FORCE IS ABOUT THE SAME EVERYWHERE ON EARTH SO THE WEIGHT OF AN OBJECT IS ABOUT THE SAME AS ITS MASS

6. Forces… In order for an unbalanced force to occur there must be three things…… – Giver: gives the push or the pull – Receiver: Receives the push or the pull – Effect: The end result of the force

7. Friction – force that opposes motion Friction occurs between two surfaces that are touching. – Depends on type of surface and the force that is pushing the surfaces together. SANDPAPER = GREATER FRICTION ICE = LOWER FRICTION MORE MASS AGAINST THE SURFACE = GREATER THE AMOUNT OF FRICTION

8. TYPES OF FRICTION SLIDING FRICTION – SLIDING ACROSS THE FLOOR ROLLING FRICTION – ROLLING ANYTHING WITH WHEELS FLUID FRICTION – OPPOSES MOTION OF AN OBJECT THROUGH A FLUID – GASES OR LIQUIDS STATIC FRICTION – When force is applied but motion does not occur