What will be the value of acceleration due to gravity on the surface of the earth if the radius of the earth suddenly decreases to 60% of its present value, keeping the mass of the earth unchanged ?

27.25 m/s²

 From Newton’s law of gravitation, we have ; 

Gravitational Field : g = (Gx  M₁)/R²

Since the radius is reduced to 60% of its original value;

The new radius R’ = 0.6 x R

Therefore;

g’ = (G x M₁)/(0.6*R)²

g’ = g/(0.6)²

    = 9.81 / (0.6 x 0.6)

g’ = 27.25 m/s².