JEE Main202122 Jul 2021Morning ShiftPhysicsWork, Power and EnergyActual
A porter lifts a heavy suitcase of mass 80 kg and at the destination lowers it down by a distance of 80 cm with a constant velocity. Calculate the work done by the porter in lowering the suitcase. (take g = 9 . 8 ms - 2 )
Options
- A- 62720 . 0   J
- B- 627 . 2   J
- C+ 627 . 2   J
- D784 . 0   J
Correct answer
B. - 627 . 2   J
Step-by-step solution
W Porter   + W mg = ΔK . E . = 0   W Porter   = - W mg = - m g h = - 80 × 9 . 8 × . 8 = - 627 . 2   J