What is weightlessness ? Explain with example.

When a weight of the body becomes zero or when any surface exerts a force on a body and reaction force becomes zero then this body is said to be in weightlessness position.

When a spring balance hang through a ceiling and on its other end, mass of body suspended the length of spring increases and from this we can know the weight of body.

Now, when a spring fall freely, the spring is not stretched at all, the weight of body is not notable. This phenomena is known as weightlessness.

$(i)$ The resultant weight of person in a lift when the lift is in free fall motion,

$\mathrm{W}=m g-m a$

$\text { but } a=g$

$\therefore \mathrm{W}=m g-m g$

$\mathrm{~W}=0$

$\therefore$ When the weight of person becomes zero this position is known as weightlessness.

$(ii)$ The acceleration of the every parts of the satellite is towards the centre of earth when it revolves. Thus, acceleration of this is equal to the acceleration due to gravity at that place. Hence, everything in the satellite will be in weightlessness position, all are in free fall state. Resultant force $\mathrm{F}=m g^{\prime}-m a_{c}$

(Centripetal acceleration $a_{c}=$ acceleration due to gravity at that place) $\therefore \mathrm{F}=0$