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A porter lifts a heavy suitcase of mass 80 \mathrm{~kg} and at the destination lowers it down by a distance of 80 \mathrm{~cm} with a constant velocity. Calculate the workdone by the porter in lowering the suitcase.
(take \mathrm{g}=9.8 \mathrm{~ms}^{-2} )
 
Option: 1 -62720.0 \mathrm{~J}
Option: 2 -627.2J
Option: 3 +627.2 \mathrm{~J}
Option: 4 784.0 \mathrm{~J}

Answers (1)

best_answer

As the suitcase lowering is done with the constant velocity
\therefore$ Net force $=0
Fext =m g
Work done =\left(F_{\text {ext }}\right) s \cos \left(180^{\circ}\right)

                \begin{aligned} &=(\operatorname{mg}) s(-1) \\ &=(80 \times 9.8)(0.8)(-1) \\ &=-627.2 \mathrm{~J} \end{aligned}                 

The correct option is (2)

Posted by

vishal kumar

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