Key words: Friction, physics, physical science, walking, writing, pencil, eraser, ice, automobile brakes, tires, coefficient, sliding, rolling, lubrication, energy waste, heat, loss, wear, shoe, sole, Ron Kurtus, School for Champions. Copyright © Restrictions

# Uses of Friction

by Ron Kurtus (revised 11 April 2015)

Although you normally hear about trying to reduce or eliminate friction, it actually has some important uses.

Since friction is a resistance force that slows down or prevents motion, it is necessary in many applications where you might want to hold items or do things and prevent slipping or sliding. In those cases, there is an advantage of having friction.

Quite often uses of frction can be seen from how things would be without friction. Without friction, you would not be able to walk, drive a car, or hold objects. Pens and pencils would not work.

Stopping a car or bike (brakes)

Questions you may have include:

• How is friction important in walking?
• How is friction used in writing?
• How is friction important in vehicles?

This lesson will answer those questions. Useful tool: Units Conversion

## Walking

You could not walk without the friction between your shoes and the ground. As you try to step forward, you push your foot backward. Friction holds your shoe to the ground, allowing you to walk. Consider how difficult it is to walk on slippery ice, where there is little friction.

Bear did not heed warning sign

## Writing

Writing with a pencil requires friction. You could not hold a pencil in your hand without friction. It would slip out when you tried to hold it to write. The graphite pencil led would not make a mark on the paper without friction.

A pencil eraser uses friction to rub off mistakes written in pencil lead. Rubbing the eraser on the lead wears out the eraser due to friction, while the particles worn off gather up the pencil lead from the paper.

## Driving a car or riding a bicycle

Your car would not start moving if it wasn't for the friction of the tires against the street. With no friction, the tires would just spin.

Likewise, you could not stop without the friction of the brakes and the tires.

## Summary

Friction is necessary in many applications to prevent slipping or sliding.

Observe little things around you

## Resources and references

Ron Kurtus' Credentials

### Websites

Friction Concepts - HyperPhysics

Friction - Wolfram Research Science World

Friction Resources - Extensive list

### Books

The following books are available from Amazon.com.

#### Basic

Complete Idiot's Guide To Physics by Johnnie T. Dennis; Alpha (2003) \$18.95

What Is Friction? (Ages 4-8) by Lisa Trumbauer; Children's Press (CT) (2004) \$4.95

Friction Science and Technology (Mechanical Engineering Series) by Peter J. Blau; Marcel Dekker Pub. (1995) \$89.95

Physics of Sliding Friction (NATO Science Series E:) by B.N. Persson, E. Tosatti; Springer Pub. (1996) \$358.00

Do you have any questions, comments, or opinions on this subject? If so, send an email with your feedback. I will try to get back to you as soon as possible.

## Students and researchers

www.school-for-champions.com/science/friction_uses.htm

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