Due to rotation of earth the effective acceleration due to gravity $g^{\prime }=g-R{\omega }^2{\mathrm{c}\mathrm{o}\mathrm{s}}^2\lambda .$

For a given point on the surface of earth $g$ decreases as $\omega$ increases. The angular speed of earth is maximum at equator hence, the value of $g$ on the surface of the earth is smallest.