If a man on the equator of Earth stood on a scale, how would the scale read compared to the scale reading for an identical man standing on the equator of a non-rotating Earth?

A. It would read less than on the non-rotating Earth
B. It would read the same as on the non-rotating Earth
C. It would read greater than on the non-rotating Earth
D. It would depend on where the man is

Question

If a man on the equator of Earth stood on a scale, how would the scale read compared to the scale reading for an identical man standing on the equator of a non-rotating Earth?  

A. It would read less than on the non-rotating Earth
B. It would read the same as on the non-rotating Earth
C. It would read greater than on the non-rotating Earth
D. It would depend on where the man is

anonymous · Answer

Another thing mentioned earlier in the problem:

The radius of the Earth(rotating) is actually 0.1% greater than at the poles.

anonymous · Answer

I know that if we looked purely at the force of gravity, that the force would be greater, and therefore scale would read larger, on the non-rotating planet due to the smaller radius.  Isn't there additional centripital acceleration acting on the man on the rotating Earth though?

vincent-lyon.fr · Answer

You are almost there, I think.

You mentioned two effects that would change the result.
Do they add up? if yes, in which direction?
Do they counteract? In that case, which is stronger?

anonymous · Answer

Rethinking it I determined that regardless of whether the Earth is rotating or not, the only forces acting  the men are gravity and normal.  

A fraction of the gravitational force exerted on the man on the rotating planet is required to change his velocity and keep his motion circular.  Is this true?  I'm thinking this would mean that mg (and therefore the normal force and the scales reading) would be less on the man on the rotating planet.

vincent-lyon.fr · Answer

True, on the rotating Earth, gravity is slightly more than the normal force. So scale reading would be less for that reason.
What about the 'bigger' radius?

anonymous · Answer

The difference in radius isn't large enough to significantly change the gravitational force?

vincent-lyon.fr · Answer

Well, the effect of the rotation of Earth is also extremely small, even at the equator.

anonymous · Answer

I'm not sure then.  The question seems qualitative due to the lack of information.

vincent-lyon.fr · Answer

Yes it is! Re-read my first post carefully.

anonymous · Answer

c

ujjwal · Answer

taking centrifugal force into account, the gravity on rotating earth is lesser ... Now, here you are not concerned with radius since you are not comparing weights at equator and poles. well, even if you would be concerned about radius, the force of gravity is still less at equator due to larger radius.. 
$$F=GMm/r ^{2}$$