Certain force acting on a 20 kg mass changes it's velocity from 5 ms–1 to 2 ms

Question:

Certain force acting on a 20 kg mass changes it's velocity from 5 ms–1 to 2 ms–1. Calculate the work done by the force.

Answer:

Mass of the object m = 20 kg

Initial velocity u = 5 ms^–1

Final velocity v = 2 ms^–1

Work done = change in kinetic energy

W = 1/2 mv²- 1/2 mu²

W = 1/2 m(v² - u²)

W = 1/2 X 20(2² - 5²)

W = 10 X (4-25)

W = -210J

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