Weightlessness - By Aditya Abeysinghe

Weightlessness is the absence of stress or strain resulting from external forces, as usually experienced by a person or simply occurs when there is no force of support on your body.

Weightlessness is a concept, in which the person who is experiencing it experiences,

                        1. .Zero weight

                        2. Free fall

Weightlessness can occur due to several reasons:

            

     1. In a satellite

E.g.: Assume a satellite of mass ‘m’ orbiting around a planet of mass M at a distance R from the center of the planet.

The acceleration of the spacecraft and astronaut (mass m₁) are both g₀ in magnitude, where g₀ is the acceleration due to gravity at a distance R. If S is the reaction of the surface of the spacecraft in contact with the astronaut, then, for circular motion,

F = m₁g₀ – S = m₁a =m₁g₀ 

Thus, S = 0

Thus, the astronaut now does not experience any reaction from the surface of contact with the spacecraft. Hence, the astronaut experiences “weightlessness”.

1.       

      2. In a lift which falls in free fall

E.g.: Consider a person of mass m travelling in a lift. The weight of the person is mg, since he/she is interacting with the Earth’s gravitational field. 

However, when the lift is in free fall, the apparent weight of the object given by,

F = ma

Mg - W_apparent = Mg, makes it zero. 

Thus, the person although accelerating downwards, experiences free fall and hence experiences “weightlessness” (Since the force of gravity cannot be felt without any other opposing forces, you would have no sensation of it).