Terminal Velocity and Friction Due to Air

claimed by cshimkus3

Acceleration of Falling Objects

When you drop an object from a certain height off the ground, you can observe that the speed of the object does not remain constant throughout that object's free fall. The object's speed changes as it falls and we know from the momentum principle that this is due to a net force acting on the object( Fnet = dp/dt ). If you drop an object from a tall enough starting height, you can also observe that the acceleration of the object is not constant either, so one can conclude that the net force on the object is not constant. An object falling towards the Earth's surface will not accelerate indefinitely, but will reach what is called ' ' terminal velocity ' '.

Falling Objects in a Vacuum

The zeroth law states that if two systems are at thermal equilibrium at the same time as a third system, then all of the systems are at equilibrium with each other. If systems A and C are in thermal equilibrium with B, then system A and C are also in thermal equilibrium with each other. There are underlying ideas of heat that are also important. The most prominent one is that all heat is of the same kind. As long as the systems are at thermal equilibrium, every unit of internal energy that passes from one system to the other is balanced by the same amount of energy passing back. This also applies when the two systems or objects have different atomic masses or material.

Friction Due to Air

If A = B and A = C, then B = C A = B = C

Where does that energy go?

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A Graphical Interpretation

The first law of thermodynamics defines the internal energy (E) as equal to the difference between heat transfer (Q) into a system and work (W) done by the system. Heat removed from a system would be given a negative sign and heat applied to the system would be given a positive sign. Internal energy can be converted into other types of energy because it acts like potential energy. Heat and work, however, cannot be stored or conserved independently because they depend on the process. This allows for many different possible states of a system to exist. There can be a process known as the adiabatic process in which there is no heat transfer. This occurs when a system is full insulated from the outside environment. The implementation of this law also brings about another useful state variable, enthalpy.

Examples

Reversible process: Ideally forcing a flow through a constricted pipe, where there are no boundary layers. As the flow moves through the constriction, the pressure, volume and temperature change, but they return to their normal values once they hit the downstream. This return to the variables' original values allows there to be no change in entropy. It is often known as an isentropic process.

Irreversible process: When a hot object and cold object are put in contact with each other, eventually the heat from the hot object will transfer to the cold object and the two will reach the same temperature and stay constant at that temperature, reaching equilibrium. However, once those objects are separated, they will remain at that equilibrium temperature until something else acts upon it. The objects do not go back to their original temperatures so there is a change in entropy.

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History

Thermodynamics was brought up as a science in the 18th and 19th centuries. However, it was first brought up by Galilei, who introduced the concept of temperature and invented the first thermometer. G. Black first introduced the word 'thermodynamics'. Later, G. Wilke introduced another unit of measurement known as the calorie that measures heat. The idea of thermodynamics was brought up by Nicolas Leonard Sadi Carnot. He is often known as "the father of thermodynamics". It all began with the development of the steam engine during the Industrial Revolution. He devised an ideal cycle of operation. During his observations and experimentations, he had the incorrect notion that heat is conserved, however he was able to lay down theorems that led to the development of thermodynamics. In the 20th century, the science of thermodynamics became a conventional term and a basic division of physics. Thermodynamics dealt with the study of general properties of physical systems under equilibrium and the conditions necessary to obtain equilibrium.

See also

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References

https://www.grc.nasa.gov/www/k-12/airplane/thermo0.html http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/thereq.html https://www.grc.nasa.gov/www/k-12/airplane/thermo2.html http://www.phys.nthu.edu.tw/~thschang/notes/GP21.pdf http://www.eoearth.org/view/article/153532/