Weightlessness - Practice Questions & MCQ

There are basically three cases of weightlessness -

1. When objects fall freely under gravity -

           When a man is in a free-falling lift, then he will feel the weightlessness.

       2.When a satellite revolves in its orbit around the earth -

           Because of this, the astronauts will feel weightlessness in the satellite.

       3.  When bodies are at null points in outer space -

              As we go up from the earth’s surface the gravitational pull of the earth goes on decreasing and the gravitational pull of the moon’s increasing. There is a point when both the gravitational force will be equal and opposite, that null the weight of the body and we feel weightlessness.

Weightlessness in a Satellite.

The acceleration of the satellite is $\frac{G M}{r^2}$ towards the centre of the earth.
Let us suppose a body of mass m placed on a surface inside the satellite moving around the earth.
Then force on the body are -
(i) The gravitational pull of earth $=\frac{G M m}{r^2}$
(ii) The reaction by the surface $=R$

By Newton's law $\frac{G m M}{r^2}-R=m a$

$
\frac{G m M}{r^2}-R=m\left(\frac{r^2 M}{r^2}\right) \quad \therefore \quad R=0
$
 

As the reaction becomes 0.

And from the Laws of motion, we know that the reaction on a body will give its weight.

So, the body will feel weightlessness in the satellite.