A.4 Estimation of radial or centripetal forces on the Earth’s crust
From Appendix 2 consider a 1M3 of crust with an average density of 2.8 x103 Kg.m-3.
Taking the same values used in Appendix 2
ρ = Average density of the crust: 2.8 kg.m-3
M = Mass of 1M3 of element of crust: 2.8 x103kg
R = Radius of Earth (m): 6.4x106 metres
ω = Angular velocity (rad s-1): 7.27x10-5 rads.sec-1
Thus, Fr = Radial Outward Force (N)
= M ω2.R
= 2.8 x 103 x (7.27 x10-5)2 x 6.4 x106
= 94.71 N
= c 9.65 kgf
Thus, for every 1 Tonne of Crust, the Outward Force at the Equator due to the rotational velocity = 9.65/ 2.8 = c. 3.4 kg
This is equivalent to a 0.034% reduction in weight compared with that at the poles, where the rotational velocity is zero. This is enough to cause the crustal plates to move around the Earth surface on a frictionless mantle.