An 800 kg car is traveling on a horizontal road; it then accelerates. During the

Question

An 800 kg car is traveling on a horizontal road; it then accelerates. During the acceleration,
the engine did 4.65 x 104 J of work on the car; the combined force of air resistance and roliing
friction did-2.14 x 104 J of work on it.
a) Didthe kinetic energy of the car increase or did it deuease? By how much?
b) Did the speed of the car increase or did it decrease? By how much? (Hinl Since it's the change in kinetic energy that's being calculated, the initial kinetic energy can be taken to be 0 J.)

Explanation / Answer

we have, a Net work done = change in Kinetic energy KE = (4.65-2.14) x 10^4 = 2.51 x 10^4 J Kinetic energy has clearly increased !!! b. Speed will also increase as KE = 0.5mv^2

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