Force of earth gravity on 1 kg mass is 9.8 N.
Since the mass is at earth surface, therefore its distance from the centre of earth is equal to the radius of the earth i.e. 6400 km.
The force of earth gravity is calculated as
F=GMm/r^2 =(6.67*〖10〗^(-11)*6*〖10〗^24*1)/〖(64*〖10〗^6)〗^2 =9.8 N
