if radius of the earth (assuming perfect sphere)is decreased keeping its mass constant ,effective value of g will increase at poles while may increase or decrease at equator.WHY??
g = G*M / R^2 The value of g changes from place to place due to the elliptical shape of the Earth and the rotation of the Earth. Due to the shape of the Earth, g is inversely proportional to the square of the radius. It is least at the equator and maximum at the poles, since the equatorial radius (6378.2 km) is more than the polar radius (6356.8 km)