Cov khoom no yog cov hlua khi - duab txhuam cov lus ua los ntawm kev sib txhuam ua phooj ywg thiab cov neeg sib txhuam ib puag ncig ua ke thiab muaj zog tiv thaiv, muaj lub zog siab. Nws yog tsuas yog siv rau lub braking ntawm cov tshuab hnyav xws li cov nkoj thiab cov khoom siv mining. Cov khoom tau zoo heev - qhov kub tsis kam, coj tus nqi tsawg thiab ruaj khov txhuam meefficient.
