Question

The diagram shows a section through the station.
The passengers who use the station are carried from platform level to street level in a lift.

Explain why these passengers gain gravitational potential energy in the lift, even when they are below ground.

Answer 1

Answer:

GPE = mgh; when using this equation, h refers to the change in height.

Passengers have moved to a higher point when they are carried from platform level to street level.

Since gravitational force still acts underground, work is done on the passengers against gravity to lift them to a higher point.

(ii) The tunnel is designed so that the trains go up a slope as they enter the station and go down a slope as they leave. The driver uses brakes to stop the train in the station and a motor to make the train move away. Explain how the sloping parts of the tunnel affect the amount of work that needs to be done on the train by the brakes and by the motor