A backpack is lifted vertically at constant speed from the floor of a classroom to a…
PHYSICS · Multi-part · A Level · Physics · Mechanics and materials · Mechanics and materials
Problem
A 4.0kg backpack is lifted vertically at constant speed from the floor of a classroom to a storage shelf 1.8m above the floor. Neglect air resistance.
(a) Calculate the work done by the gravitational force on the backpack as it is raised to the shelf. Show all work and include appropriate units.
(b) Determine the change in gravitational potential energy of the backpack–Earth system during the lift, taking the floor as the zero-potential reference level.
(c) Compare the numerical results of parts (a) and (b). Explain how their signs and magnitudes are consistent with the principle of energy conservation for the backpack–Earth system.