I was studying about circular motion and found a topic that is apparent weight and found an equation of apparent value of g.


But I can't understand why this is written


  • 1
    $\begingroup$ see the diagram-the body is rotating with our earth and the rotational motion leads to a centrifugal force in earth's frame of reference, therefore the body will experience two forces-one due to g and another due to w^2r and the resultant of two forces is effective wt. $\endgroup$
    – drvrm
    Aug 29, 2018 at 18:25
  • $\begingroup$ do you mean to say that the calue of resultant is less than its constituent vectors. Why?? $\endgroup$
    – Naman Vyas
    Aug 29, 2018 at 19:25
  • $\begingroup$ Related and all you need to do is use the cosine rule to get a relationship between the three sides of the vector triangle. physics.stackexchange.com/q/328618/104696 $\endgroup$
    – Farcher
    Aug 29, 2018 at 22:35

1 Answer 1


Check the force diagram at the equator from the inertial coordinate system:

$mg-N= m\omega^2R$.

So $mg>m\omega^2R$ or $g>\omega^2R$.

Obviously $2g>\omega^2R$.

This is a necessity to keep us from flying off the earth.

  • $\begingroup$ You are right but will there be further more explanation. $\endgroup$
    – Naman Vyas
    Sep 1, 2018 at 3:54
  • $\begingroup$ The first equation is the second law for a body in circular motion with angular velocity $\omega$. The other two equations are just some arithmetic. The final statement provides the physical basis. Could you say which part requires additional explanation? $\endgroup$
    – npojo
    Sep 1, 2018 at 6:35

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