Verified Answer :

vbv

suppose earth is a soid sphere which will attract the body towards its centre.So, acc. to law of gravitation force on the body will be,
F=Gm1m2/R^2
but we now that F=ma
and here accleration(a)=accleration due to gravity(g),so
force applied by earth on will also be mg
replace above F in formula by mg and solve,
F=G
mEm/R^2                             ( here mE is mass of earth and m is mass of body)
mg=G
mEm/R^2
so,
g =G*mE/R^2




suppose earth is a soid sphere which will attract the body towards
its centre.So, acc. to law of gravitation force on the body will be,
F=Gm1m2/R^2
but we now that F=ma
and here accleration(a)=accleration due to gravity(g),so
force applied by earth on will also be mg
replace above F in formula by mg and solve,
F=G
mEm/R^2                             ( here mE is mass of earth and m is mass of body)
mg=G
mEm/R^2
so,
g =G*mE/R^2