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Work, Energy And Power

Question

A person is walking on horizontal road with a load on his head. Is he doing any work? Explain.

Solution

We know,
Work done, $W equals F with rightwards arrow on top times S with rightwards arrow on top$
In this case gravitational force is acting in vertically downward direction and displacement is in horizontal direction.
Therefore angle between $space space F with rightwards arrow on top space a n d space S with rightwards arrow on top$ is $90 degree.$
$W equals F s space cos 90 degree space equals space 0$
Hence, work done by the person is zero.