The velocity of a car increase from 54 km/hr to 72km/hr l. How much is the work done if the mass of the car is 1500 kg?
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One can apply the work-energy theorem for the problem and propose that the work done(W) on the body(car) must be equal to the change in kinetic energy (K.E.)as no info about dissipative forces like friction etc. are given.
>>> W = Final K.E. - Initial K.E. = (1/2) m. {V^2 -u^2},
where m is the mass of the car and v and u are its final and initial velocities.
as 1 km/hour = 1000 m/60x60 s = 5/18 m/s,
u= (54)x(5/18 )m/s = 15 m/s ; u^2 = 225 (m/s)^2 ,
similarly v = 72 x (5/18 )m/s = 20 m/s and v^2 = 400 (m/s)^2
Therefor W = (1/2) x 1500 kg x { 400 - 225 } (m/s)^2 = (750 x 175 ) kg.(m/s)^2
>>>> work done(W) = 131 250 joules
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