Physics I For Dummies
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In a physics equation, given initial velocity, time, and acceleration, you can find an object’s displacement. Here’s an example: There you are, the Tour de France hero, ready to give a demonstration of your bicycling skills. There will be a time trial of 8.0 seconds. Your initial speed is 6.0 meters/second, and when the whistle blows, you accelerate at 2.0 m/s2 for the 8.0 seconds allowed. At the end of the time trial, how far will you have traveled?

You could use the relation s = (1/2)at2, except you don’t start off from zero speed — you’re already moving, so you should use the following:

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In this case, a = 2.0 m/s2, t = 8.0 s, and vi = 6.0 m/s, so you get the following:

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You write the answer to two significant digits — 110 meters — because you know the time only to two significant digits. In other words, you ride to victory in about 110 meters in 8.0 seconds. The crowd roars.

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Dr. Steven Holzner has written more than 40 books about physics and programming. He was a contributing editor at PC Magazine and was on the faculty at both MIT and Cornell. He has authored Dummies titles including Physics For Dummies and Physics Essentials For Dummies. Dr. Holzner received his PhD at Cornell.

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