Physics 2011 JAMB Past Questions - Question 4: A man standing on a lift that is descending does not feel any weight because

Correct Answer

A

Explanation

When a person is standing on a lift that is descending at a constant velocity, they do feel their normal weight, just as they would if they were standing on the ground. However, they may not perceive this weight in the same way they would when the lift is at rest or moving at a constant velocity.

The sensation of weightlessness in an elevator or lift typically occurs when the lift is accelerating, whether upward or downward. This feeling is due to the physics of the situation.

1. **At Rest or Constant Velocity**: When the lift is not accelerating (neither ascending nor descending), the person inside the lift feels their normal weight. This is because the force of gravity acting on the person is balanced by the normal force exerted by the floor of the lift.

2. **Descending at a Constant Velocity**: When the lift is descending at a constant velocity, the person still feels their normal weight. This is because the forces acting on them remain balanced, just as they do when at rest. The person and the lift are both falling together, so there is no relative acceleration between them.

3. **Feeling of Weightlessness During Acceleration**: The feeling of weightlessness occurs when the lift is accelerating. When the lift accelerates downward, it momentarily reduces the normal force exerted by the floor. This makes it seem as though the person is floating inside the lift, as if they are in freefall. Similarly, when the lift accelerates upward, they may feel heavier than usual due to an increased normal force.

In summary, a person standing in a descending lift doesn't feel any weight change as long as the lift is moving at a constant velocity. The sensation of weightlessness or increased weight occurs during periods of acceleration or deceleration.