1. FRICTION A force that resists the movement or tendency to move between two objects in contact

2. Draw in the friction vector.Ff

3. What factors affect friction?
the roughness of the surfaces
the amount of force being applied to the surfaces

4. Scroll down to find static friction animation.
Simulation
Scroll down to find static friction animation.

5. Static friction force A force is applied but the object doesn’t move
No relative motion = net force = 0
The friction force is in the opposite direction of the applied force

6. Static Friction FN
Ff (Ffs) FP FW
Net Force = Zero

7. Kinetic friction force
A force is applied and the object moves but friction slows it down
The friction force is in opposite direction to the motion
Kinetic friction exists between the two moving surfaces
Notice: The size of the friction force is smaller than the size of the pushing force when accelerating.

8. Kinetic Friction AcceleratingFN
Ff (Ffk) FP FW
Net Force ≠ Zero

9. Kinetic Friction Constant VelocityFN
Ff (Ffk) FP FW
Net Force = Zero

10. on a horizontal surface
Friction equation
Ff = μ FN
FN = FW
on a horizontal surface

11. Coefficients of Friction
μs = coefficient of static friction μk = coefficient of kinetic friction

12. Static Friction Force Maximum magnitude is Fsf = μs FN
Direction = opposite of applied force

13. Kinetic Friction Force
Magnitude is Fkf = μk FN
Direction = opposite of applied force

14. Free Fall
The motion of a body when only the force of gravity is acting on the body.
Technically only in space.
Usually means without a parachute or other devise to slow motion.
Includes upward motion after launching force is removed.

15. Air Resistance
When an object moves through air it runs into air molecules.
It is a type of friction because it resists the motion of the object.

16. A special situation
The object stops accelerating and travels at constant velocity.
FA = FW and Fnet = 0
Terminal velocity

17. A special situation
When the FA = FW
Fnet = 0 FA FW

18. Terminal Velocity https://www.youtube.com/watch?v=p0IZsfzDS4s
Scroll down even more

19. Classwork/Homework
Static Friction Problems