Data Bases • Custom Term Papers • Free Term Papers • Free Research Papers • Free Essays • Free Book Reports • Plagiarism? Links • Top 100 Term Paper Sites • Top 25 Essay Sites • Top 50 Essay Sites • Search 97,000 Papers @ DirectEssays.com • Search 101,000 Papers @ ExampleEssays.com • Search 90,000 Papers @ MegaEssays.com Free Essays • Term Paper Sites • Chuck III's Free Essays • Free College Essays • TermPaperSites.com • My Term Papers • Get Free Essays • Essay World • Planet Papers	Search Lots of Essays Back to Subjects - Physics how tires work how tires work they are not really round. There is a flat spot on the bottom where the tire meets the road. This flat spot is called the contact patch. This helps the tire have more space on the ground so that the square inch area touching the ground is higher. By doing this, You don’t need as much pressure in the tire. Tires usually only need 30 pounds per square inch. You can figure out how much four tires can hold by adding the square inches touching the ground and multiplying it by four (all tires). Then you must add in the area pressure of all the tires. You find this by finding the area of the tire in square inches and multiplying that by 30. Tire manufacturers sometimes publish a coefficient of rolling friction (CRF) for their tires. You can use this number to calculate how much force it takes to push a tire down the road. The CRF has nothing to do with how much traction the tire has; it is used to calculate the amount of drag or rolling resistance caused by the tires. The CRF is just like any other coefficient of friction: The force required to overcome the friction is equal to the CRF multiplied by the weight on the tire. This table lists typical CRFs for several different types of wheels. Tire Type Coefficient of Rolling Friction Low-Rolling Resistance Car Tire 0.006-0.01 Let's figure out how much force a typical car might use to push its tires down the road. Let's say our car weighs 4,000 pounds (1814.369 kg), and the tires have a CRF of 0.015. The force is equal to 4,000 x 0.015, which equals 60 pounds (27.215 kg). Now let's figure out how much power that is. If you've read the How Stuff Works article How Force, Torque, Power and Energy Work, you know that power is equal to force times speed. So the amount of power used by the tires depends on how fast the car is going. At 75 mph (120.7 kph), the tires are using 12 horsepower, and at 55 mph (88.513 kph) they use 8.8 horsepower. All of that power is turning into heat. Most of it goes into the tires, but some of it goes into the road (the road actually bends a little when the car drives over it). From these calculations you can see that the three things that affect how much force it takes to push the tire down the road (and therefore how much heat builds up in the tires) are the weight on the tires, the speed you drive and the CRF (which increases if pressure is decreased). If you drive on softer surfaces, such as sand, more of the heat goes into the ground, and less goes into the tires, but the CRF goes way up. Bibliography: Word Count: 493
Copyright © 1998-2008 College Term Papers, INC All Rights Reserved. DMCA Notifications and Requests