1. FORCES

2. What do we mean when we say force? A force = a push or pull upon an object resulting from the object’s interaction with another object. All forces between objects can be placed into two catergories – Contact forces – Forces resulting from action “at a distance”

3. Kinds of forces Contact forces Applied force (push) Frictional force Tension force (pull) Normal force (push) Air resistance Elastic force Action at a distance forces Gravitational force Electrical force Magnetic force

4. Drawing Free Body Diagrams -Represent the object with a dot: -Arrows represent forces acting on the object. -The length of the arrow represents the amount of force: - The direction of the arrow shows the direction that the force is acting.

5. Drawing Free Body Diagrams Each force arrow in the diagram is labeled to indicate the exact type of force: F push f friction F Gravitational F Normal, F Tension F Electrostatic F magnetic -Label each Force acts On object and By object

7. Sky Diver in free fall F f Friction force on Diver by Air F g Gravitational force on diver by earth

9. Sky Diver in parachute F t tension force on diver by parachute harness F g gravitational force on Diver by earth

10. Bull Dog pushing a skate board. Diagram the forces acting on the skateboard.

11. Skateboard pushed by dog F g Dog + F g skateboard gravitational force on skate board by earth F p Pushing force on skateboard by dog F f friction force on skateboard by street F N Normal force on skateboard by street

12. Dog on Ramp At rest

13. Dog on ramp F g gravitational force on dog by earth friction force on dog by ramp F f F N Normal force on dog by ramp

16. F N Normal force on climber by rock F T Tension force on climber by rope F g Gravitational force on Climber by earth Forces on Rock Climber

17. Draw the forces acting on the ball

18. Forces on Basket Ball F g Gravitational force on Ball by earth F P Pushing force on ball by Michael Jordan F f friction force on ball by hand

19. Draw the forces acting on the football.

20. Forces on Foot Ball F g Gravitational force on Ball by earth f F f friction force on ball by air resistance

21. Graham needs to redo the image. A force diagram for a crate being dragged across the floor is shown. The sizes of each of the horizontal forces are shown in the diagram. 1. What is the size and direction of the NET force on the crate? 2. If the acceleration of the crate is 2.5 m/s/s, what is the mass of the crate?