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Work, Power And Energy
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05/11/2021 10:50 am
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Calculate the work done by the brakes of a car of mass 1000 kg when its speed is reduced from 20 m/s to 10 m/s.
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05/11/2021 10:52 am
Mass of car = 1000 kg
Initial velocity, u = 20 m/s
Final velocity, v = 10 m/s
Retardation = a
Distance covered = s
Using third equation of motion
v2 – u2 = 2as
as = -150
Work done, W = Fs
F = ma
W = mas
as = -150
W = (1000)(150) = -150 kJ
Negative sign shows that the brakes are acting on the opposite direction of motion.