Acceleration in Drag RacingDate: 06/06/2002 at 02:21:18From: Tim FraserSubject: drag racing

A drag race car starts from a dead stop. It travels 1/4 mile in 11.0 seconds. What is the MPH formula?

Every time I try to figure out the answer I come up with an average speed. As if the speed were the same at finish as it was at start!

I realize it must be some type of curve, but I never took trig or calc.Any help would be greatly appreciated. Thanks, Tim

Date: 06/06/2002 at 14:31:48From: Doctor IanSubject: Re: drag racing

Hi Tim,

Assuming that the acceleration is constant (which it probably isn't!), the equation would be

distance = (1/2) * acceleration * time^2

For your example, that's

5280/4 feet = (1/2) * a * (11 sec)^2

5280/4 feet a = --------------- (1/2) 121 sec^2

= 21.8 feet/sec^2

So after 1 second, it's going about 22 feet per second. After 2 seconds, about 44 feet per second. After 11 seconds, it would be going 242 feet per second... which is about

60 miles/hour 242 feet/second * -------------- = 165 miles/hour 88 feet/second

Does this help?

- Doctor Ian, The Math Forum http://mathforum.org/dr.math/