##### I need some help with this equation

label Algebra
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The stopping distance d of an automobile is directly proportional to the square of its speed v. A car required 45 feet to stop when its speed was 60 miles per hour. Find a mathematical model that gives the stopping distance d in terms of its speed v. It also wants me to do this problem ---->( Estimate the stopping distance if the brakes are applied when the car is traveling at  miles per hour.)

Oct 22nd, 2017

Since stopping distance d is directly proportional to the square of the speed of the car, then we the following relationship:

d = kv^2  where k is the proportionality constant

Given that the car required 45 feet to stop when its speed was 60 miles per hour, we can find then find k:

45 = k(60^2)

k = 45/3600 = 0.0125

So then the equation becomes

d = 0.0125v^2  for any speed

For the problem you want to solve just plug the speed into the equation and you'll get the stopping distance d.

Apr 28th, 2015

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Oct 22nd, 2017
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Oct 22nd, 2017
Oct 23rd, 2017
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