Question

calculate the force of gravitation due to earth on a ball of 1 kg mass lying on the ground (mass of earth = 6×10²⁴ kg, radius of earth = 6.4 × 10³ km, and G=6.7 × 10-¹¹ Nm²/kg²)​

Answer 1

Distance between centre,  r = Radius of earth

of earth and ball                    = 6.4 x 10³ x 1000 m

                                               = 6.4 x 10⁶ m

Now, putting these values in the above formula, we get:

                                            F = 6.7 x 10⁻¹¹ x 6 x 10²⁴ x 1 / (6.4 x 10⁶)²

                     or                   F = 9.8 newtons

Thus the earth exerts a gravitational force of 9.8 newtons on a ball of mass 1 kilogram. This is a comparatively large force. It is due to this large gravitational force exerted by earth that when the 1 kg ball is dropped from a height, it falls to the earth.