Question

An object of mass 5 kg falls from rest through a vertical distance of 20 m and attains a velocity of 10 m/s. How much work is done by the resistance of the air on the objrct? (g=10m//s^(2)).

Answer 1

The correct answer id -750 joules

Explanation:

Since, we know from work energy theorem that , work done by all forces is equal to the kinetic energy. Thus,

or Wmg  +Wair =  (1/2)mv^2

Work done by air= (1/2)mv^2- Wmg ⇒ equation (1)

So,

Wmg=mgh

Putting in equation 1

work done by air = (1/2)mv^2- mgh

Thus, substituting values in , we get

work done by air (Wair) = (1/2)×5×(10)^2  −(5)×(10)×(20)

Hence, the work done by air is equal to −750J

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Answer 2

Answer:

the correct answer is -750 joules.

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