# Estimation of Equatorial Bulge of the Earth [duplicate]

My dynamics lecture notes repeat the Earth's equatorial bulge can be approximated as: $$\approx \frac{\Omega^2R}{g} \approx \frac{1}{300}$$ (Do they mean R/300?)

They also include statements like:

"The Earth's oblateness $\frac{I_3-I_1}{I_1}\approx \frac{\Omega^2R}{g} \approx \frac{1}{300}$"

Could anybody explain where this comes from? I have tried several ways to balance the gravitational and centripetal forces but I never seem to arrive at the correct result and cannot get my head around this concept.

• Possible duplicates: physics.stackexchange.com/q/8074/2451 and links therein. – Qmechanic Mar 26 '18 at 20:41
• @Qmechanic indeed that answered my question, thank you! Should I delete my post to keep the site clean or should I keep it as future reference if somebody has the same question but cannot locate the other post? – Jhonny Mar 26 '18 at 20:51
• The latter is preferred, but you decide. – Qmechanic Mar 26 '18 at 20:54
• Please keep this. The prior answers are exceptionally detailed, and this dimensional/order-of-magnitude estimate is very good (most Datum have an inverse flattening: $298 < 1/f < 301$). – JEB Mar 26 '18 at 23:28