Ib hom zawv zawg qhov rooj haum rau siv nyob hauv nruab nrab ntawm kev kaw lus, tsis xaiv qhov chaw thov, tsis muaj ib qho chaw thov khoom, cov khoom siv qub
Barn qhov rooj sib txig rau ntawm phab ntsa muaj qee qhov kev thov, yog tias cov ntaub ntawv sib tsoo, yog tias cov khoom siv ua npuas dej tsis zoo, nws tau muab cov pob zeb zoo nkauj ua ke Cov khoom kho vajtse ntawm cov khoom siab dua, qhov zoo dua cov hlau ntim rub smoother thiab lub suab tsis tshua muaj siab xav tau, yuav nruab pendulum nyob rau hauv lub qhov rooj {}}
