A porter carries a suitcase of mass on his head while walking steadily along a…
PHYSICS · Multi-part · CBSE · Physics · Work and Energy · Work and Energy
Problem
A porter carries a suitcase of mass 20kg on his head while walking steadily along a horizontal floor and then climbs a stationary escalator to a height of 4.0m. Treat the suitcase as the system of interest and ignore air resistance.
(i) For the horizontal walk, state whether the work done on the suitcase by (a) the porter’s muscular force and (b) the gravitational force is positive, negative or zero. Give clear reasons for each answer.
(ii) For the upward ride on the escalator, state the sign of the work done on the suitcase by (a) the porter’s muscular force and (b) the gravitational force. Justify your choice in each case.
(iii) Explain why carrying a load at constant height on level ground is considered tiring even though, in the physics sense, the muscular force does no mechanical work.
(iv) Write the SI unit of work and state whether work is a scalar or a vector quantity.