What is the magnitude of the gravitational force between the earth and a 1 kg object on its surface? (Mass of the earth is 6 × 1024 kg and radius of the earth is 6.4 × 106 m)

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 × 10²⁴ kg

Mass of object, m = 1 kg

Universal gravitational constant, G = 6.7 × 10⁻¹¹ Nm² kg⁻²

Since the object is on the surface of the Earth,

r = radius of the Earth (R)

r = R = 6.4 × 10⁶ 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