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# Friction

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##### Description:

Students will compare and contrast friction- this includes experimentally.

This is your notes; be sure to stop, rewind, and rewatch as much as necessary.

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Tutorial

Here is the video for your notes. Be sure to pause, rewind, and stop as necessary.

Source: Langhans and various educators

1. Friction is defined as _____________________________________________________

2. Friction occurs when the ________________ and _______________ of two surfaces touch against each other.

3. The amount of friction depends on two factors…_________ and _________

4. Rougher surfaces typically have:       MORE       LESS     friction.  (circle one)

5. There is typically:      MORE     LESS     friction between a heavy object and another  surface than there is between a light object and another surface.

6. The two basic types of friction include __________________ friction, which is the friction that exists between two surfaces that are not moving and __________________ friction, which is the friction that exists between surfaces that are moving.

7. Generally, ____________________ friction is greater than sliding friction.

8.    Rank these types of friction, greatest amount first, least amount last

Kinetic (sliding)           Static

a. _____________________   b. ____________________

9. Explain how ball bearings reduce friction _________________________________

10. Explain how friction is useful in brakes and tires.  __________________________

11. In each of the following situations, what effect will the change have on the amount of friction?  Use the following choices: a) increase b) decrease c)no change

____________) The normal force (force pushing surfaces together) increases

____________) The roughness of only one surface is increased

____________) The surface area in contact increases

____________) A lubricant is added between the surfaces

____________) Static friction changes to kinetic friction

Questions – Fill In

12.  Name a variable that has no effect on friction. ______________________________

13.  Which direction does the frictional force always act?  ______________

14. Name two ways that friction is harmful….__________________and _________________________________

15. Name two ways that friction is helpful…..________________ and ________________________________

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