Newtonian Physics
Definitions
Section titled “Definitions”Momentum
Section titled “Momentum”Momentum is defined as the product of body’s mass by its velocity:
Impulse
Section titled “Impulse”Impulse is the change in momentum over a period of time:
Also,
(only at a constant acceleration, see Newton’s second law in impulse form)
Newton’s Laws of Motion
Section titled “Newton’s Laws of Motion”Fist Law
Section titled “Fist Law”A body remains at rest, or in motion at a constant speed in a straight line, unless it is acted upon by a force
Second Law
Section titled “Second Law”Object’s acceleration is directly proportional to the net force acting on it and inversely proportional to its mass
Objects with constant mass
Section titled “Objects with constant mass”Objects with constant mass and acceleration
Section titled “Objects with constant mass and acceleration”Third Law
Section titled “Third Law”If two bodies exert forces on each other, these forces have the same magnitude but opposite directions
Law of Conservation of Momentum
Section titled “Law of Conservation of Momentum”In a closed system (one that does not exchange any matter with its surroundings and is not acted on by external forces), the total momentum remains constant (does not change over time)
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From Newton’s third law:
…meaning the sum of invidual bodies’ momentum does not change over time, leading to conclusion that
Applicability
Section titled “Applicability”- the law can also be applied in non-closed systems over a short period of time if external forces affecting system’s bodies are negligible in this period of time
- the law can be applied in non-closed systems to axes which are not affected by external forces (for example, the horizontal plane of motion of a falling body is unaffected by gravity)