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To explain the irreversible thermodynamic processes, the scientists formulated the second law of thermodynamics. The second law of thermodynamics explains what processes can occur in the universe and what processes cannot happen. One scientist named R. J. E. Clausius (1822-1888) made the following statement:

Naturally, heat moves from high-temperature objects to low-temperature objects; naturally, heat does not proceed from low-temperature object to high-temperature object (Second law of thermodynamics—Clausius’s statement).

Clausius’s statement is one of the special statements of the second law of thermodynamics. It is called special statement because it only applies to one process just, related to heat transfer. Since this statement is not related to other processes, we need a more general statement. The development of a general statement of the second law of thermodynamics is based on the study about heat engine. Therefore, we discuss heat engine first.

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Article Thermodynamic processes : Isothermal Adiabatic Isochoric Isobaric

There are four thermodynamic processes, namely Isothermal, isochoric, isobaric and adiabatic processes.

Isothermal Process (constant temperature)

In an isothermal process, system temperature is kept constant. Theoretically, the analyzed system is an ideal gas. Ideal gas temperature is directly proportional to ideal internal gas energy (U = 3/2 n R T). T does not change, so U also does not change. Thus, if applied to the isothermal process, the first law of the thermodynamic equation becomes:

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Thermodynamic process

Heat (Q) is the energy that moves from one object to another because of the temperature difference. About systems and environments, heat is energy moving from system to environment or energy moving from environment to system, due to the temperature difference. If the system temperature is higher than the ambient temperature, heat will flow from the system to the environment. If the ambient temperature is higher than the system temperature, then heat flows from the environment to the system.

Heat (Q) is energy that moves due to the temperature difference, whereas work (W) is related to energy transfer through work. For example, if the system does work on the environment, then energy moves from system to environment. Conversely, if the environment does work on the system, then energy moves from environment to system.

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Isku dhacyada aan la qabsan karin

Sharciga ilaalinta tamarta dhaqdhaqaaqa laguma dabaqi karo isku dhaca aan laalaaban karin. Sharciga ilaalinta xawaaraha ayaa lagu dabaqi karaa isku dhaca aan laalaaban karin haddii aan xoog dibadda ah uusan ku shaqeyn labada shay ee isku dhacaya. Isku dhaca aan laalaaban karin, laba shay ayaa isku dheggan ama isku dheggan ka dib isku dhaca.

Tusaale ahaan su'aal 1aad.

Laba shay ayaa isku miisaan ah, kuwaas oo kala ah 1 kg. Shayga 1aad wuxuu ku socdaa diyaarad fidsan xawaare dhan 10 m/s wuxuuna la dhacaa shayga labaad oo nasasho ku jira. Shilka ka dib, labada shay ayaa isku dheggan. Waa maxay xawaaraha labada shay ka dib shilka?

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Isku dhacyo qayb ahaan dabacsan

Isku dhacyada qayb ahaan laastikada ah, sharciga ilaalinta xawaaraha ayaa la dabaqi karaa, halka sharciga ilaalinta tamarta dhaqdhaqaaqa aan la dabaqi karin. Marka isku dhac dhaco, xoogaa tamar dhaqdhaqaaqa ah ayaa loo beddelaa tamar dhawaaq, tamar kulayl, iyo tamar gudaha ah. Isticmaalka ereyga laastikada wuxuu tilmaamayaa in ka dib isku dhaca, labada shay aysan isku dheganayn laakiin ay ka soo boodayaan.

Tusaale ahaan isku dhaca qayb ahaan dabacsan waa isku dhaca hal-cabbir ah ee laba marmar ama laba kubbadood oo barkad ah.

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Ilaalinta xawaaraha toosan

Sharciga ilaalinta dhaqdhaqaaqa toosan wuxuu dhigayaa in haddii uusan jirin awood dibadeed oo ku shaqeysa laba shay oo is-jiidaya, xawaaraha walxaha ka hor shilku wuxuu la mid yahay xawaaraha walxaha ka dib shilka.

p₁ +p₂ =p₁ '+ p₂ ' ……………………….. Isle'egta 1.4

m₁ v₁ +m₂ v₂ = m₁ v₁ '+ m₂ v₂ '

Haddii labada shay ay isku dhegaan ka dib shilka,

m₁ v₁ +m₂ v₂ = (m₁ +m₂ ) v'

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Shilalka dabacsan ee si fiican u socda

A collision of two objects is called a perfectly elastic collision if the momentum or kinetic energy of each object before the collision is equal to the momentum and kinetic energy of each object after the collision. In other words, the conservation of momentum law and conservation of kinetic energy law are applicable in perfectly elastic collisions. The use of the word elastic signifies that after the collision, the two objects do not stick together or are not attached to each other but bounce off. The momentum of each object is conserved.

The momentum of each object is conserved.

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Mabda'a tamarta shaqada-farsamada

Aragtida tamarta shaqada-kinetic-ga waxay sheegaysaa in shaqada shabakada ama shaqada ay qabato xoogga saafiga ah ay la mid tahay isbeddelka tamarta kinetic-ga.

W_net = KU_t – KU_o = 1⁄2 m(v)_t² - v_o²)

W_net = Waxaa jira laba nooc oo awood ah, kuwaas oo kala ah xoog muxaafid ah, iyo xoog aan muxaafid ahayn. Sidaa darteed, shaqada saafiga ah waxaa loo qaadan karaa inay ka kooban tahay shaqada ay qabato ciidan muxaafid ah iyo shaqada ay qabato ciidan aan muxaafid ahayn.

W_c +W_nc = ΔKE

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Shaqada ay qabtaan ciidamada muxaafidka ah Tamarta suurtagalka ah

Observe an object which moves vertically upwards and then return to its initial position after reaching a maximum height. When the object is moving vertically upwards, weight does negative work on the object. When the object is moving upwards, the object’s height increases. Therefore, the object’s gravitational potential energy increases as well. It can be concluded that the negative work done by weight is equal to the increase in the object’s gravitational potential energy (PE).

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Ciidanka muxaafidka ah iyo ciidanka aan muxaafidka ahayn

1. Conservative Force

1.1 Miisaanka (w)

Observe an object which moves vertically upwards until reaching a maximum height before moving downwards towards its initial position. When moving vertically upwards by h, the weight is opposite in direction from displacement. Thus, the weight does negative work on the object. 

W = w h (cos 180^o) = – w h = – m g h

After reaching a maximum height, the object moves downwards towards its initial position by h. When moving downwards, the weight is in the same direction as the displacement. Because it is in the same direction as displacement, the weight does positive work.

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