Question

How is acceleration due to gravity calculated?

Answer 1

Its calculated by performing Cavendish Experiment

you can also do it by allowing an object to fall through height H and calculate the time t

and use the formula

T=√2H/g

(but keep in mind that u will have some error due to air resistance and other factors)

Answer 2

F = GMm/r2

G - Gravitational constant

M - Mass of earth

m - Mass of body

R - Distance between their center of mass

GM/r2 is constant on any planet

We know the values of G M and r

Plug these in the equation and viola we get the familiar g = 9.8 m/s2