Question

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). 

Answer 1

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

= / 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 

= / 2 = 6.7 × 10⁻¹¹ × 6 × 10²⁴ × 1 / (6.4 × 106) 2 = 9.8