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.