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  • A girl is carrying a school bag of 3 kg mass on her back and moves 200 m on a levelled road. The work done against the gravitational force will be (g =10 m s^–2) (a) 6 ×103 J (b) 6 J (c) 0.6 J (d) zero

A girl is carrying a school bag of 3 kg mass on her back and moves 200 m on a levelled road. The work done against the gravitational force will be (g =10 m s^{-2})

(a) 6 \times 10^3 J

(b) 6 J

(c) 0.6 J

(d) zero

Answers (1)

Answer:  [D]

Solution.

We know that work is defined as:
W=Fd\cos \theta

As the girl is carrying a schoolbag of 3 kg, the girl must be applying force in vertically upward direction against gravity.
The displacement of the girl is in the horizontal direction, as it is moving on a level road.
The angle between force and displacement is 90^{\circ}.
Therefore, by the formula, work done by the girl against gravity will be zero.
W=Fd\cos 90^{\circ}=0

Hence, the correct answer for this question is option D.

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infoexpert26

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