Drag Racing - Involving Work and Velocity

[marcus1255]

Homework Statement

The problem reads:

"You are stopped at a red light, an identical car to yours pull up alongside. When the light turns green, you and the other car accelerate at a constant rate, but the other car's acceleration is greater. You see another stop light ahead and know you will have to stop at the light, so you accelerate from 0 to 20 mph for half the distance and then brake slowly so you decelerate for the last half, you observe this takes you a total of 30 seconds. The other car accelerates from 0 to 40 mph for the first half of the distance and brakes for the last half. Both cars traveled the same distance, starting from rest and ending at rest. You want to know how much work your car engine did compared to the other car and how much work your brakes did compared to the other car"

Homework Equations

Acceleration = change in velocity / change in time
Work = Force x Distance

The Attempt at a Solution

I am not really sure where to start..

 

[Delphi51]

Convert to metric units. Do the motions one at a time, beginning with the acceleration from 0 to 20. There evidently is no friction loss, so you can just use energy formulas like KE = ½mv².