Question

The loss of potential energy of an elevator coming down from the top of the building to a stop at the ground floor is

• A. lost to the driving motors
• B. converted into heat
• C. lost in friction of moving surfaces
• D. used up in lifting up counter weight

Hint:

In mechanical systems like elevators, potential energy is often converted into heat energy due to friction in the machinery.

Answer 1

The Correct Option is B

Step 1: Understand the principle of energy conversion.
When the elevator moves down, its potential energy is converted to other forms of energy. Potential energy (\(PE\)) is given by: \[ PE = mgh \] where:
\(m\) is the mass of the elevator,
\(g\) is the acceleration due to gravity,
\(h\) is the height from which the elevator is coming down.
This potential energy has to be dissipated as the elevator moves downward.
Step 2: Analyze the possible conversions of potential energy.
The potential energy of the elevator is lost during its descent. The most common form of energy conversion in mechanical systems like elevators is heat generated by friction in the moving parts (such as the motor, pulleys, and cables).
Step 3: Evaluate the choices.
Option (1): "Lost to the driving motors" is incorrect, as the motor is typically involved in lifting the elevator, not in dissipating potential energy when it descends.
Option (3): "Lost in friction of moving surfaces" is partly correct but doesn't fully account for all energy conversion in this system.
Option (4): "Used up in lifting up counterweight" is incorrect, as the counterweight assists in the lifting process and is not directly involved in energy dissipation during descent.
Option (2): "Converted into heat" is the most appropriate choice because, during the descent, the potential energy is primarily converted into heat energy due to friction in the elevator system.
Thus, the correct answer is that the potential energy is converted into heat.