Cov Lus Qhia Txog Physics Yooj Yim

Txhawm rau piav qhia txog cov txheej txheem thermodynamic uas tsis rov qab tau, cov kws tshawb fawb tau tsim txoj cai thib ob ntawm thermodynamics. Txoj cai thib ob ntawm thermodynamics piav qhia txog cov txheej txheem twg tuaj yeem tshwm sim hauv lub ntiaj teb thiab cov txheej txheem twg tsis tuaj yeem tshwm sim. Ib tug kws tshawb fawb hu ua RJE Clausius (1822-1888) tau hais cov lus hauv qab no:

Ntuj tsim teb raug, cua sov txav ntawm cov khoom kub siab mus rau cov khoom kub qis; ntuj tsim teb raug, cua sov tsis mus ntawm cov khoom kub qis mus rau cov khoom kub siab (Txoj cai thib ob ntawm thermodynamics - Clausius cov lus).

Cov lus ntawm Clausius yog ib qho ntawm cov lus tshwj xeeb ntawm txoj cai thib ob ntawm thermodynamics. Nws hu ua cov lus tshwj xeeb vim nws tsuas yog siv rau ib qho txheej txheem xwb, cuam tshuam nrog kev hloov pauv cua sov. Vim tias cov lus no tsis cuam tshuam nrog lwm cov txheej txheem, peb xav tau cov lus dav dav dua. Kev tsim cov lus dav dav ntawm txoj cai thib ob ntawm thermodynamics yog raws li kev kawm txog cov cav cua sov. Yog li ntawd, peb tham txog cua sov ntawm lub cav ua ntej.

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Tsab Xov Xwm Txog Cov Txheej Txheem Thermodynamic: Isothermal Adiabatic Isochoric Isobaric

Muaj plaub txoj kev thermodynamic, uas yog Isothermal, isochoric, isobaric thiab adiabatic.

Txheej Txheem Isothermal (kub tas li)

Hauv ib txoj kev isothermal, qhov kub ntawm lub cev tseem nyob ruaj khov. Hauv kev xav, lub cev uas tau soj ntsuam yog ib qho roj zoo tagnrho. Qhov kub ntawm cov roj zoo tagnrho yog qhov sib piv ncaj qha rau lub zog roj zoo tagnrho sab hauv (U = 3/2 n RT). T tsis hloov pauv, yog li U kuj tsis hloov pauv. Yog li, yog tias siv rau txoj kev isothermal, txoj cai thawj zaug ntawm qhov sib npaug thermodynamic dhau los ua:

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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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Kev Sib Tsoo Tsis Sib Haum

Txoj cai txuag lub zog kinetic tsis siv tau rau hauv kev sib tsoo tsis sib luag. Txoj cai txuag lub zog momentum siv tau rau hauv kev sib tsoo tsis sib luag yog tias tsis muaj lub zog sab nraud ua rau ob yam khoom sib tsoo. Hauv kev sib tsoo tsis sib luag, ob yam khoom lo ua ke lossis txuas rau ib leeg tom qab kev sib tsoo.

Piv txwv lo lus nug 1.

Ob yam khoom muaj tib lub cev hnyav, uas yog 1 kg. Yam khoom 1 txav mus rau ntawm ib lub dav hlau tiaj tiaj nrog qhov ceev ntawm 10 m/s thiab tsoo nrog yam khoom thib ob uas tsis txav. Tom qab kev sib tsoo, ob yam khoom lo ua ke. Qhov ceev ntawm ob yam khoom tom qab kev sib tsoo yog dab tsi?

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Kev sib tsoo ib nrab elastic

Hauv kev sib tsoo uas muaj qee qhov elastic, txoj cai ntawm kev txuag lub zog momentum siv tau, thaum txoj cai txuag lub zog kinetic tsis siv tau. Thaum lub sijhawm sib tsoo tshwm sim, qee lub zog kinetic raug hloov mus ua lub zog suab, lub zog cua sov, thiab lub zog sab hauv. Kev siv lo lus elastic qhia tias tom qab kev sib tsoo, ob yam khoom tsis lo ua ke tab sis dhia tawm.

Ib qho piv txwv ntawm kev sib tsoo ib nrab yog qhov kev sib tsoo ib-seem ntawm ob lub pob zeb lossis ob lub pob pas dej ua ke.

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Kev txuag ntawm linear momentum

Law of conservation of linear momentum states that if there is no external force acting on two colliding objects, the momentum of the objects before the collision is equal to the momentum of the objects after the collision.

p₁ +p₂ = paj₁ ’ + p₂ ’ ………………….. Equation 1.4

m₁ v₁ +m₂ v₂ = kuv₁ v₁ ' + m₂ v₂ '

If after collision both objects stick together,

m₁ v₁ +m₂ v₂ = (m₁ +m₂ ) v'

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Kev sib tsoo zoo kawg nkaus elastic

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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Lub hauv paus ntsiab lus ntawm lub zog ua haujlwm-khoom siv tshuab

The work-kinetic energy theorem states that the net work or the work done by the net force is equal to the change in kinetic energy.

W_net = KE_t – MUS RAU_o = 1⁄2 m(v_t² -v_o²)

W_net = There are two types of forces, namely conservative force, and non-conservative force. Thus, net work can be considered to be comprised of the work done by a conservative force and the work done by a non-conservative force.

W_c + W_nc = ΔKE

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Cov haujlwm ua los ntawm cov zog txuag hluav taws xob

Saib ib yam khoom uas txav mus rau saum ntuj thiab tom qab ntawd rov qab mus rau nws qhov chaw pib tom qab ncav cuag qhov siab tshaj plaws. Thaum yam khoom txav mus rau saum ntuj, qhov hnyav ua haujlwm tsis zoo rau yam khoom. Thaum yam khoom txav mus rau saum ntuj, qhov siab ntawm yam khoom nce ntxiv. Yog li ntawd, lub zog gravitational potential ntawm yam khoom kuj nce ntxiv thiab. Nws tuaj yeem xaus lus tias qhov haujlwm tsis zoo uas ua los ntawm qhov hnyav yog sib npaug rau qhov nce ntawm lub zog gravitational potential (PE).

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Lub zog tiv thaiv thiab lub zog tsis tiv thaiv

1. Conservative Force

1.1 Qhov hnyav (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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