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The net work needed to stop this car is gonna be equal to its change in kinetic energy that's what we know from the textbook work net equals change in kinetic energy. So that's ½ 'mv' final squared minus ½ 'mv' initial squared. The final speed is zero so we can say this term is gone and for this case we have the work net is negative ½ 'mv' initial squared. Let's substitute in numbers we have negative ½ times the mass of the car 1,250 kilograms times 105 kilometers per hour times 1 hour for every 3,600 seconds times 1,000 meters for every kilometer and we'll square that result that's converting to meters per second there. Then we have negative ANSWER joules. For the sixth edition the mass of the car is one, sorry fifth edition I should say is 1,000 kilograms and it's instead going at 110 kilometers per hour. So multiply by the same conversion factors there and result for the fifth edition is negative ANSWER joules.
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