WikiMechanics

Bidang, Iban people. Sarawak 20th century, 50 x 101 cm. Lintah motif. From the Teo Family collection, Kuching. Photograph by D Dunlop.

Let Ψ = ( … P_i … P_f … ) be a sequence of events in the history of particle P characterized by a change of momentum ∆ p and elapsed time ∆ t between events P_i and P_f . Definition: the force acting on P is

This relationship is a restatement of Newton's second law, "The change of motion is proportional to the motive force impressed; and is made in the direction of the right line in which that force is impressed."¹

Theorem: when interactions with P can be characterized using a mass m for which changes are negligible, then

where a is the acceleration.

Change of Momentum due to an Absorption Process

Let Ψ = ( … P_i … P_f …) be a sequence of events that describes a process where particle X is absorbed by particle P between events P_i and P_f

Momentum is conserved, so that

Therefore the change in momentum of P is

Recall that if P is not a point particle, and if the frame-of-reference is inertial, and events are in-phase with each other, then

so that

Then the change of inertia for P is proportional to the momentum of the absorbed particle X

Change of Momentum due to an Emission Process

Classification of Aethereal Particles by their Momenta

Let P be an aethereal particle described in a frame-of-reference F. If F is inertial then the momentum of P depends on its inertia as follows.

Momentum	Inertia of P	Examples	WikiMechanics role
	I = 0	Xt Xb	exchange quanta for the gravitational force
	Ie ≠ 0	eº eº	exchange quanta for the electric force
	Im ≠ 0	µº µº	exchange quanta for the magnetic force
	Iw ≠ 0	wº wº	exchange quanta for the weak force