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Have you ever taken a ride on a roller coaster or on a giant wheel in an amusement park?


During the fast downward and upward movement on a giant wheel, how did you feel?


It’s wondrous!!. You feel as if you are falling freely without having any weight. This is due to the phenomenon of weightlessness.


You appear to have lost your weight when you move down with a particular acceleration. Sometimes, you feel the same while travelling in a lift.


Whenever the person in a lift moves down with an acceleration (\(a\)) equal to the acceleration due to gravity (\(g\)), i.e., when a = g, this motion is known as ‘Free fall’. Here, the apparent weight (\(R\ =\ m\ (g–g)\ =\ 0\)) of the person is zero. This condition or state is known as state of weightlessness.


The same effect occurs while falling freely on a roller coaster or a swing or in a giant vertical wheel. You experience an apparent weight loss and weight gain when you move up and down in such rides.


Weightlessness of the astronauts:


Some of us believe that the astronauts in the orbiting space station do not experience any earth’s gravitational force. So they float. But this doesn’t seem right.


Astronauts are not floating but falling freely around the Earth due to their huge orbital velocity. Since space stations and astronauts have equal acceleration, they are under free-fall conditions. Hence, both the astronauts and the space station are in a state of weightlessness.


Application of Newton’s law of gravitation:


  1.  Dimensions of the heavenly bodies can be measured using the gravitation law. Mass of the Earth, the radius of the Earth, acceleration due to gravity, etc., can be calculated with higher accuracy.
  2.  It helps in discovering new stars and planets.
  3.  One of the irregularities in the motion of stars is called ‘Wobble’ lead to the disturbance in the motion of a planet nearby. In such conditions, the mass of the star can be calculated using the law of gravitation. 
  4.  It helps to explain germination of roots is due to the property of geotropism which is the property of a root responding to gravity. 
  5.  It helps to predict the path of the astronomical bodies.