Question

What do you mean by work? Give an example of negative work done. What is the work to be done to increase the velocity of a car from 18 km/h to 90 km/h if the mass of the car is 2000 kg





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Answer 1

Answer:

Work done is negative when there is negative displacement in direction of applied force. For e.g. the work done by frictional force against a moving body.

Given,

Mass of the car = 2000kg

Let u = 18km/hr = 5m/s.

Let v = 19km/hr = 5.3m/s.

Work done(W.D) = Change in Kinetic Energy of the car

=>( 1/2 mv2 - 1/2 mu2)

=> 1/2m (v2 - u2)

=> 1/2 x 2000( 5.3m/s2 - 5m/s2 )

=> 1000kg x 0.3m/s2

=> 300kgm/s2(or) 300 J