Q 11-05-149JEE MainJEE Main 2021 (22 Jul, Shift 1)Easy
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 $g = 9.8\ \text{m s}^{-2}$)
Answer: (B) −627.2 J
At constant velocity the porter pushes up with force $mg$ while the suitcase moves down 0.8 m: $W = -mgh = -80\times9.8\times0.8 = -627.2$ J.
Solution by Sreeraj P, M.Sc Physics