## With brakes applied, a 1340 kg car decelerates from 94.0 km/hr. What is the work done by the braking force in bringing the car to a stop?

Question

Find the car’s kinetic energy, KE. The work needed to bring it to a stop will be -KE. This assumes the braking force is the only force acting on the car in the direction it is traveling.

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General Physics
4 years
1 Answer
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## Answer ( 1 )

Since the force causes the car to stop, the work is equal to the car’s initial kinetic energy.

1 km = 1000 m, 1 h = 3600 s, 1 km/h = 1000/3600 = 5/18 m/s

v = 94 * 5/18 = 470/18

This is 26 1/9th m/s.

KE = ½ * 1340 * (470/18)^2 = 1.48003 * 10^8 ÷ 324

This is approximately 4.57 * 10^5 J.