The force of gravity between tim and john is 1.85 x 10^-9 n. if they are 18 m apart and tim has a mass of 120 kg, what is john’s mass ?

75kg    

Explanation:

Given:

Force of gravity(F) = 1.85 x 10⁻⁹N

distance between Tim and John = 18m

Mass of Tim = ?

Unknown:

Mass of John = ?

Solution

Newton's law of universal gravitation states that every particle of matter in the universe attracts every other particle with a force that is directly proportional to the product of the masses of the particles and inversely proportional to the square of the distance between them.

i.e                            

                          F =G

let

                     m₁ represent mass of Tim

                     m₂ mass of John

                    G is the universal gravitation constant = 6.67 x 10⁻¹¹Nm²kg⁻²

                    r is the distance seperating them

The unknown is m₂ and we should make it the subject of the expression:

               m₂  = F x

m₂ =

m₂ = 75kg      

it's all four options.