Physics
Physics
Problem
A porter moves a suitcase between two points within the same building. The initial point A is on the ground floor and the final point B is on the first floor, situated vertically 4.0 m above A. The porter may choose any route inside the building – for example, a straight lift ride, or a long sloping ramp that spirals upward. Answer the following: a. (i) What is meant by the work done by a force between two specified points? b. (ii) The porter first walks horizontally 12 m, then climbs the ramp rising uniformly through 4.0 m along a 25 m path. Would the work done by the gravitational force during this motion depend on the horizontal segment? Give reasons. c. (iii) A friend claims that taking the lift (which rises vertically 4.0 m) makes the gravitational force perform less work than walking up the ramp. Evaluate this claim with proper justification.Intuitive explanation
The key insight here is recognizing that gravitational potential energy depends only on vertical height, not on the path taken. No matter whether the porter takes a direct elevator, a spiraling ramp, or any other route, the change in gravitational potential energy is determined solely by the vertical displacement of 4.0 m. This is why we call gravity a conservative force—the work done against it to raise the suitcase depends only on the starting and ending heights, making the route irrelevant for energy calculations.
Intuitive explanation
The key insight here is recognizing that gravitational potential energy depends only on vertical height, not on the path taken. No matter whether the porter takes a direct elevator, a spiraling ramp, or any other route, the change in gravitational potential energy is determined solely by the vertical displacement of 4.0 m. This is why we call gravity a conservative force—the work done against it to raise the suitcase depends only on the starting and ending heights, making the route irrelevant for energy calculations.