Download Spinning Earth and gravity

Spinning Earth and gravity
QUESTION:
If the Earth stopped spinning then what is the weight of the Earth and the weight of a body on it
Answer:
The fact that the Earth is spinning has no effect on its own mass. The phenomena of weight
requires there to be another object to which the Earth is attracted towards. Strictly speaking we
cannot talk about the WEIGHT of the Earth, only its MASS.
However a body placed on the surface of the Earth will have weight due to the gravitational
attraction of the Earth. If the Earth is spinning there will be a tendency for this object to fly off the
surface in a tangential straight line. Some of the gravitational pull of the Earth will be required to
produce a centripetal force on the object to keep it moving in a circle with the Earth as the Earth
spins. This means that its effective weight is slightly less than if the earth were not spinning.
So if the earth stopped spinning the measured weight of a body would increase – but ever so
slightly!
You can observe an effect similar to this by considering what will happen to the weight of a body as
it is moved from the equator to the poles. Its weight would increase slightly since the radius of the
circle in which it is rotating is decreasing. (This is true even if the non-spherical nature of the earth
is ignored)