Swiss mathematician Leonhard Euler formulated two laws to describe the motion of a rigid body relative to an inertial reference frame. The first law describes how applied forces change the velocity of the center of mass of a rigid body. The second law describes how the change in angular momentum of a rigid body is influenced by the moment of the applied force and any attachments to other bodies an object may have. These laws were written for bodies of fixed matter. That is the body must be composed of a fixed amount and type of matter that does not change.

The first of Euler's two laws is written as F = d/dt(G) where F is each individual force applied to the body and G is the linear momentum of the body. This form is written relative to an inertial reference...