universal gravitation problem

Question

Tom has a mass of 87 kg. He and Sally are standing 37 m apart. What is Sally’s mass if the force of gravitational attraction between them is 5 x 10^-10 N?

Answer 1

Let m₁ = Tom's mass and m₂ = Sally's mass

The attractive force, F = Gm₁m₂/d^2,

Where G = 6.67x10^-11 [Nm²/kg²] is universal gravitational constant and d = distance between Tom and Sally

Making the Sally's mass the subject of the relation and plugging in the numbers, you get

m₂ = d²F/Gm₁ = (37m)²(5x10^-10N)/((6.67x10^-11 Nm²/kg²)(87kg)) = 117.96kg