Teoiric chlasaiceach na n gas , ina nglactar leis an gas mar bhailiuchan de chaithnini comhionanna. Geilleann siad do dhlithe meicnice Newton , agus deanann imbhuailti leaisteacha le cheile is le ballai an tsoithigh iata ina bhfuil siad. Tri dhlithe na meicnice a chur ag obair, chomh maith le staitistic , is feidir gaolta idir gluaisni na gcaithnini is airionna teirmidinimiciula toirte an ghais (bru, teocht is eile) a dhiorthu. [1] [2]