Why Sri Lanka has low gravity:
Proximity to Equator: The Earth's rotation creates a centrifugal force that is strongest at the equator, slightly counteracting gravity, making equatorial regions naturally have lower gravity than the poles.
Indian Ocean Geoid Low (IOGL): A large gravity anomaly (a "gravity hole") exists southwest of Sri Lanka, where the Earth's crust is thinner, leading to less mass beneath the surface and a weaker gravitational pull.