Fri March 18, 2011 By: Gaurav Avhad

please can u explain me the concept of gravity at different position on the earth by showing the animation of earth and explaining the change in g at various position like equator pole and how the axis of earth is tilted and from where does the earth move from equator or something like that?

Expert Reply
Fri March 18, 2011
Dear student,
Gravity is the attractive force that holds our feet to the ground and keeps planets in orbit around stars. Despite the dominant role that gravity plays in human activities on Earth, it is a feeble force compared with the electrical forces that hold atoms together. For example, the gravitational attraction between an electron (a negatively charged particle in an atom) and the nucleus of an atom is 1041 (1 followed by 41 zeros) times weaker than their electrical attraction. The effects of gravity are so significant to humans on Earth because the constant downward tug we feel comes from the combined pull of every atom that makes up the Earth.

Variation of g with distance measured in terms of Earth radii. Green line shows a more accurate theoretical values..

What is latitude?



Every point on the sphere lies on the same latitude, which lie on the base of the cone whose axis coincides with the polar axis and whose generators make an angle f with the horizontal or equatorial plane. The angle f is called the latitude of the place. Latitude of equator = 0o and latitude of north pole = 90o and latitude of south pole = -90o.



We can observe that if the Earth is considered to be a sphere of radius R, the radius of the smaller circle in the latitude f=Rcosf.



A particle on the latitude f which is undergoing uniform circular motion with angular velocity 'w', experiences centripetal acceleration  directed towards the centre of the small circle OI. This acceleration 'a' can be resolved into two components, tangential and vertical.

Gravitational acceleration 'g' acts on the body.



Since all the forces acting on the body at the latitude f result in uniform circular motion, the net of all forces should be equal to centripetal force.

At the equator,

At the pole,

Hence, the gravitation acceleration is maximum at the poles and minimum at the equator.
Hope this helps.
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