According to the universal law of gravitation, gravitational force exerted on an object of mass m is given by

𝐹 = {𝐺𝑀𝑚 \over 𝑟^2}

Where,

Mass of Earth, M = 6 × 10^{24} kg

Mass of object, m = 1 kg

Universal gravitational constant, G = 6.7 × 10^{−11} Nm^{2} kg^{−2}

Since the object is on the surface of the Earth,

*r *= radius of the Earth (R)

*r *= R = 6.4 × 10^{6} m

Therefore, the gravitational force

𝐹 = {𝐺𝑀𝑚 \over 𝑟^2} = {6.7 × 10^{−11} × 6 × 10^{24} × 1 \over (6.4 × 10^6)^2} = 9.8 N