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Work, Energy, Power and Collision — JEE physics STD 12 Science — Question

CBSE BoardEnglish MediumSTD 12 ScienceJEE physicsWork, Energy, Power and Collision1 Mark
Question
Assertion : A person working on a horizontal road with a load on his head does no work.
Reason : No work is said to be done, if directions of force and displacement of load are perpendicular to each other.
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Answer

(a) The work done, $W=\vec{F} \cdot s=F s \cos \theta$, when a person walkonahorizontalroad with load on his head then $\theta=90^{\circ}$.Hence $W=F s \cos 90^{\circ}=0$Thus no work is done by the person.

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