During a parade, a father carries his young child on his shoulders. The father does no work during the parade because _____________.
Choose the correct answer.

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The momentum of the child changes.

The potential energy of the child is varying.

The child's distance from the ground keeps changing.

The child's distance from the ground remains the same.

answer is D.

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Detailed Solution

We know work is given by,
W=fd cosθ
Where f is force ; d is the displacement of the body
The father exerts a force on the child in the upward direction and his displacement is in a forward direction, therefore angle between force and displacement is 90^o
W=fd cos90 =0
Hence, the work done is zero.
There is no upward or downward displacement of a child taking place that is child's distance from the ground remains the same.

Therefore, 'The child's distance from the ground remains the same.' is the correct response.

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