Static vs Sliding Friction
Thaum muaj kev sib txheeb ze lossis kev sim ntawm ob qhov chaw hauv kev sib cuag, cov rog raug tsim tawm tsam kev txav. Feem ntau cov rog no hu ua kev sib txhuam. Kev sib txhuam tshwm sim ntawm cov khoom siv, cov dej ntws, thiab ntawm cov kua / cov khoom. Kev sib txhuam hauv cov kua dej yog hu ua viscosity. Kev sib tham ntawm kab lus no feem ntau yog tsom rau kev sib txhuam rog ua rau ntawm cov khoom siv.
Ntawm Macroscopic scale, lub hauv paus chiv keeb ntawm kev sib txhuam rog yog ntaus nqi rau qhov tsis sib xws ntawm lub cev. Thaum me me qhov tsis sib xws xws li crevices thiab protrusions ntawm qhov chaw raug rau cov kev sib txheeb ze, lawv cuam tshuam ib leeg txoj kev txav los tsim cov tshuaj tiv thaiv. Muaj cov cai piav qhia txog tus cwj pwm ntawm kev sib txhuam.
1. Thaum ob qhov chaw nyob hauv kev sib cuag thiab nyob rau hauv kev txheeb ze los yog hauv kev sim ua li ntawd, ntawm qhov chaw ntawm kev sib cuag, kev sib txhuam ntawm lub cev yog qhov sib txawv ntawm kev coj mus rau kev txav ntawm lub cev.
2. Yog hais tias cov kev sib txhuam ntawm lub cev tsuas yog txaus los ua kom lub cev sib npaug, ces cov kev sib txhuam quab yuam hu ua txwv kev sib txhuam, thiab qhov loj ntawm kev sib txhuam tuaj yeem nrhiav pom qhov sib npaug.
3. Qhov sib piv ntawm qhov txwv kev sib txhuam rau qhov Nqus cov tshuaj tiv thaiv ntawm ob qhov chaw nyob ntawm cov khoom uas cov chaw tsim los ntawm thiab qhov xwm ntawm qhov chaw, tsis yog qhov loj ntawm cov tshuaj tiv thaiv ib txwm. Qhov piv yog hu ua Coefficient ntawm kev sib txhuam.
4. Qhov loj ntawm qhov txwv kev sib txhuam yog ywj siab ntawm qhov chaw sib cuag ntawm ob qhov chaw.
5. Thaum nyob hauv kev txav, kev sib txhuam quab yuam yog tawm tsam cov kev taw qhia ntawm kev txav thiab ywj siab ntawm kev tshaj tawm. Qhov sib piv ntawm qhov sib txhuam quab yuam thiab cov tshuaj tiv thaiv ib txwm nyob nruab nrab ntawm qhov chaw tseem nyob tas li thiab me ntsis tsawg dua li qhov txwv kev sib txhuam.
Microscopically, lub hauv paus chiv keeb ntawm kev sib txhuam quab yuam yog ntaus nqi rau lub zog quab yuam ntawm cov electromagnetic teb ntawm cov molecules.
Kev sib txhuam zoo li cas?
Thaum lub cev nyob rau hauv lub xeev zoo li qub (stationary), kev sib txhuam rog ua rau lub cev yog hu ua static frictional rog. Nyob rau hauv cov ntaub ntawv no, lub vector sum ntawm lub sab nraud quab yuam ua nyob rau hauv lub cev yog sib npaug zos rau qhov loj ntawm frictional rog tab sis opposite nyob rau hauv kev coj; yog li ntawd lub cev tseem nyob hauv equilibrium. Cov kev sib txhuam quab yuam nce proportional rau qhov tshwm sim sab nraud quab yuam ua rau lub cev kom txog thaum nws ncav cuag qhov txwv thiab pib txav mus. Qhov siab tshaj plaws kev sib txhuam zoo li qub yog qhov txwv kev sib txhuam.
Kev sib txhuam yog ywj siab ntawm qhov chaw sib cuag ntawm ob qhov chaw thiab nyob ntawm cov khoom siv thiab qhov xwm ntawm lub cev. Thaum qhov tshwm sim sab nraud quab yuam tshaj qhov txwv kev sib txhuam lub cev pib txav mus.
Dab tsi yog zawv zawg (Dynamic) Kev sib txhuam?
Thaum lub cev txav mus los, cov kev sib txhuam ntawm lub cev yog lub npe hu ua dynamic frictional rog. Lub dynamic frictional quab yuam yog ywj siab ntawm lub nrawm thiab acceleration. Qhov sib piv ntawm qhov sib txhuam quab yuam thiab lub zog ib txwm nyob nruab nrab ntawm qhov chaw kuj tseem nyob tas li tab sis me ntsis tsawg dua qhov piv rau qhov txwv kev sib txhuam.
Dab tsi yog qhov txawv ntawm qhov sib txhuam zoo li qub thiab zawv zawg (Dynamic) Kev sib txhuam?
• Coefficient ntawm kev sib txhuam zoo li qub me ntsis siab dua qhov coefficient ntawm kev sib txhuam dynamic
• Kev sib txhuam zoo li sib txawv ntawm qhov sib piv rau sab nraud quab yuam, thaum zawv zawg (dynamic) kev sib txhuam quab yuam nyob tas li, tsis muaj kev sib tw thiab qhov nrawm (thiab qhov tshwm sim sab nraud quab yuam).
