1. Friction

2. Motion stops because…

3. Definition A FORCE that opposes the motion of objects as they SLIDE past one another. Why didn’t the balloon cars roll forever?

4. Static friction The FORCE that acts on objects that are not moving. Static friction applies a force in the opposite direction of an applied force on an object.

5. Balloon cars that did NOT roll were unable to overcome the STATIC Friction.

6. How is static friction involved here?

7. Sliding friction The FORCE that opposes the motion of moving objects as they slide past each other. Sliding friction is LESS than static friction. This is why it is easier to slide a moving object than an object at REST.

8. The force applied is large enough to overcome the STATIC friction to get the object to move.

9. How is sliding friction involved?

10. Rolling friction The frictional force that exists when the shape of a contact point between two objects is changed to a ROUND shape.

11. This type of friction is about 100-1000 times less than STATIC or ROLLING friction.

12. How is rolling friction involved?

13. Fluid friction The force that opposes the motion of an object through a FLUID. Remember: LIQUID or GAS can be classified as fluids

14. Air resistance= fluid friction

15. Which falls faster?

16. Fluid friction in water

17. How do these reduce fluid friction?

18. What type of friction is involved?

23. How is friction being reduced?