Car deceleration problem

  • Thread starter Blade
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  • #1
Blade
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A car traveling at 45 miles per hour is brought to a stop, at constant deceleration, 132 feet from where the brakes are applied.

a. How far has the car moved when its speed has been reduced to 30 miles per hour?

b. How far has the car moved when its speed has been reduced to 15 miles per hour?

My problem here is, I am suppose to use integration (not kinematics). I'm having problems seeing where to start using integration.
 

Answers and Replies

  • #2
AD
72
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Well, you need to determine the acceleration before you can start. Use v^2 = u^2 + 2as, where v is the final velocity, u is the initial velocity and s is the displacement.

Once you've done that, you can express the velocity as a function of time

v = u + at

Integrate to find displacement

s = ut + ½at^2
 

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