LAWS OF MOTION, THERMODYNAMICS AND GAS
Newtons Laws of Motion
The three laws of motion devised by English Physicist Sir Isaac Newton (1642 - 1727) explain the basic principles which govern the movements of all objects, on Earth and in space. First published in 1687, they opened the way for the inventions and calculations that, nearly three centuries later, took man to the moon.

The laws are:
Number Law
1. A body continues in a state of rest, or in motion at constant speed in a straight line, except when this state is changed by forces acting on it.
2. Force is equal to mass multiplied by acceleration (in other words, a given force on a given mass will produce a given acceleration. On twice the mass, it will produce half the accleration. If the force on a given mass is doubled, however, the acceleration will double too.)
3. To every action there is an equal and opposite reaction.
THE FOUR LAWS OF THERMODYNAMICS.
The classic laws of Thermodynamics, which deal with the ways in which energy such as heat can be passed from one body of matter to another, were devised by several scientists during the late 19th and early 20th centuries.

The final law to be worked out was given the name of the zeroth law (bearing the number zero) because, although it was added as an afterthought, it belongs logically in front of the other three, which had by then already been given numbers.

The four laws can be summarised as:

Number Law
0. No heat will flow between any two bodies that are at the same temperature (regardless what the bodies are made of).
1. Energy can neither be created nor destroyed. So a body can gain or lose heat (or any other form of energy) only by taking it from or passing it to its environment (or to another body).
2. Heat will not pass spontaneously from a cold body to a hotter one.
3. It is impossible to cool a body right down to the temperature of absolute zero
(- 273.16 o C), the lowest possible temperature in the Universe, because to do so would require the presence of a still colder body.
All four laws are connected with the idea known as entropy, which is a measure of how much useful work can be extracted from a given system. Energy can be extracted from a system only by increasing it's degree of entropy

A hot-water bottle, for instance, filled with boiling water and placed in a cold bed, passes heat to the bed, losing its own heat in the process. But once the bottle and bed are at the same lukewarm temperature, no more useful work can be extracted from the bottle. The dissipated heat cannot be recaptured.

Since the same principle is at work in the Universe as a whole, scientists believe that the energy the Universe contains will also, eventually, be dissipated evenly and irrecoverably throughout space. This stage of maximum and universal entropy is known as the 'heat death' of the Universe.

Gas Laws
There are effectively three laws related to gases named Boyle's Law, Charles' Law and Gay-Lussec's Laws. Gay Lussec quotes two laws but the second is a paraphrase of Charles' Law.  (In the formulae, v = volume, p = pressure and T = temperature absolute).

The laws are:
 

Name Law
Boyle's Law At a constant temperature the volume of a given mass of a gas varies inversely with its pressure.

Formula =        pv = constant (if temperature T is unchanged).

 
Charles' Law Under a constant pressure the volume of a fixed mass of a gas varies directly with its absolute temperature.

Formula =        v/T = constant (if pressure p is unchanged).

 
Gay-Lussec's Laws 1. When gases combine chemically, the volumes of the reactive gases and gaseous products are in simple proportion.

Formula =        p/T = constant (if volume v is unchanged).

2. At a constant pressure all gases expand by the same amount for the same increase in temperature. (For formula see Charles' Law).
 

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