Newtonian Law of Attraction :-
Every particle of matter attracts every other particle of matter with a force which varies directly as the product of the masses of the particles and inversely as the square of the distance between them .
Let m1 gm and m2 gm be the masses of the two particles placed at a distance of the r cms . Then the force of attraction F between them is such that
F varies m1 , m2 when r is constant .
F varies 1/(r.r) when m1 , m2 are constant
Therefore by theorem of joint variation F is given by
F varies (m1m2) /(r.r)
i.e. F= gama (m1m2)/(r.r)
where gama is called constant of attraction .
So , the Newtonian law of attraction is
Attraction = gama (product of mass)/(square of distance)
-------- The attraction of a rod AB at an external point P is the same as that of the arc of a circle , of like material with center P and of radius equal to perpendicular from P on AB , which is intercepted by the lines PA and PB .