Describe the relation of boys and girls using an equation

-kx = ma

k = the strictness of the girl to keep the boy by his side

x = the distance of the boy from the girl (mental or physical)

m = the inertia of the boy (probably mental)

a = the acceleration of the boy towards the girl

 

As a result, the as the boy goes further, the acceleration of the boy towards the girl will increase and vise versa.

This rule maybe broken because another force simply becomes constantly greater then F= kx