Question

Explain in detail the idea of weightlessness using the lift as an example.

Answer 1

When a man is standing in the elevator, there are two forces acting on him.

1. Gravitational force which acts downward. If we take the vertical direction as a positive y-direction, the gravitational force acting on the man is `vec"F"_"G" = -"mg"hat"j"`

2. The normal force exerted by floor on the man which acts vertically upward, `vec"N" = "N"hat"j"`

The weightlessness of freely falling bodies: Freely falling objects experience only gravitational force. As they fall freely, they are not in contact with any surface (by neglecting air friction). The normal force acting on the object is zero. The downward acceleration is equal to the acceleration due to the gravity of the Earth, i.e., (a = g)

Newton’s second law acting on the man N = m(g – a)

a = g ∴ N = m(g – g) = 0.