A porter moves a suitcase of mass 20 kg in three successive steps:
PHYSICS · Subjective · AP · Physics 1: Algebra-based · Work Energy and Power · Work Energy and Power
Problem
A porter moves a suitcase of mass 20 kg in three successive steps:
(i) lifts it vertically upward through 1.5 m from the floor to his head,
(ii) walks forward 100 m along a horizontal platform while holding it steadily at the same height, and
(iii) lowers it vertically the same 1.5 m to place it on another surface. Assume the suitcase moves at negligible acceleration in every step and take g=9.8m s−2.
(a) For each step, calculate the work done on the suitcase by the gravitational force. State its sign clearly.
(b) For each step, calculate the work done on the suitcase by the porter’s lifting (or supporting) force. State its sign clearly.
(c) Hence obtain the total work done by (i) gravity and (ii) the porter over the entire process.