Question

♉is the gravitational acceleration calculated by GM/ R^2 correct or not..........♉​

Answer 1

The formula of gravitation by Newton is correct but when you need to calculate for bigger systems like stars and black holes, Einstein's general relativity is needed.

Answer 2

Yes it is .

Acc. to second law of motion

F = ma ( Here a = g acceleration due to gravity)

F = mg

Also

Acc. to universal law of gravitaion

F = G M m / R^2

where M is earth's mass

m is mass of body

R is radius of earth

G is gravitational constant

Note that both are equal to same force

So

mg = G Mm/R^2

g = G M / R^2