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 Action at a distance forces
Applied force (push)
Gravitational force
Frictional force
Electrical force
Tension force (pull)
Magnetic force
Normal force (push)
Air resistance
Elastic 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: Fpush ffriction FGravitational FNormal, FTension FElectrostatic Fmagnetic
-Label each Force acts On object and By object

7. Sky Diver in free fall Ff Friction force on Diver by Air
Fg Gravitational force on diver
by earth

9. Sky Diver in parachute Ft tension force on diver by parachute harness
Fg gravitational force on Diver by earth

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

11. Skateboard pushed by dog
FN Normal force on skateboard by street
Ff friction force on skateboard by street
Fp Pushing force on skateboard by dog
Fg Dog + Fg skateboard
gravitational force on skate board by earth

12. Dog on Ramp
At rest

13. FN Normal force on dog by ramp
Dog on ramp
FN Normal force on dog by ramp
friction force on dog by ramp Ff Fg
gravitational force on dog by earth

16. FT Tension force on climber by rope FN Normal force on climber by rock
Forces on Rock Climber
FT Tension force on climber by rope
FN Normal force on climber by rock
Fg Gravitational force on Climber by earth

18. FP Pushing force on ball by Michael Jordan
Forces on Basket Ball
FP Pushing force on ball by Michael Jordan
Ff friction force on ball by hand
Fg Gravitational force on Ball by earth

20. Ff friction force on ball by
Forces on Foot Ball
Ff friction force on ball by
air resistance f
Fg Gravitational force on Ball by earth

21. Graham needs to redo the image
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?