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JEE Main 202122 JulyMorning Shift
Exam
JEE Main
Year
2021
Date
22 July
Shift
Morning Shift
Subject
Physics
Chapter
Work, Power and Energy

JEE Main 2021 · 22 July · Morning Shift · Physics · Work, Power and Energy

A porter lifts a heavy suitcase of mass 80kg and at the destination...

A porter lifts a heavy suitcase of mass 80kg80kg and at the destination lowers it down by a distance of 80cm80cm with a constant velocity. Calculate the work done by the porter in lowering the suitcase. (take g=9.8ms−2g = 9 . 8{ms}^{- 2} )

Options

  1. A−62720.0J- 62720 . 0J
  2. B−627.2J- 627 . 2J
  3. C+627.2J+ 627 . 2J
  4. D784.0J784 . 0J

Correct answer

B. −627.2J- 627 . 2J

Step-by-step solution

WPorter+Wmg=ΔK.E.=0{W}_{Porter} + {W}_{mg} = \Delta K . E . = 0
WPorter=−Wmg=−mgh{W}_{Porter} = - {W}_{mg} = - mgh
=−80×9.8×.8=−627.2J= - 80 \times 9 . 8 \times . 8 = - 627 . 2J
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