Work done by a person on a book held in his hand while walking with uniform speed on a horizontal road. Here the work done is Negative, positive or zero?

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Solution

There is no force applied by the person holding a book and walking with uniform speed since to move an object with uniform speed no force is required. Work done is a product of force and displacement. Since force applied is zero in the horizontal direction no work is done.
The person also applies a vertical force on the book balancing it against the force of gravity. This force is perpendicular to the displacement of the book which is in the horizontal direction. Hence, displacement is not in the direction of the force. Thus, no work is done once again.
In total work done is zero.

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