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 Basic Thermodynamics ~ J. Pohl © ~ 2019 www.ThermoSpokenHere.com (A2500-020)

# 1.08 Momentum: BODY

The system (model of physical reality) of
Newton's Laws of Motion is the BODY.

In 1687 Newton published two axiomatic statements and three Laws of Motion. His first axiom identified "quantity of matter;" which today is called mass. Newton's (and others) used vectors and calculus to define position and velocity. Newton's Second Axiom states:

Axiom II: The quantity of motion is the measure of the same, arising from its velocity and quantity of matter, (mass) conjointly.

The modern name for Newton's "quantity of motion" is momentum and Newton's system was a BODY. Today momentum of a BODY is written as: (1) Momentum of a BODY: a vector propertyin the vector space 0XYZ

Momentum, Newton's creation, is a curious combination of two aspects of physical reality. It is said that one cannot combine "apples and oranges." But momentum is the product of mass (of the BODY) times its velocity, a vector. For velocity to be specified, one must define a coordinated space, one must understand, "vector" and one must know the basis of calculus - the derivative. Momentum, the product of a scalar and a vector, is indeed a grand idea (as Newton knew).

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