What is the difference between damping and friction? Both of them slows down any moving system. So what's the conceptual difference between them?
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1$\begingroup$ Who said there were a difference? $\endgroup$– DanielSankSep 19, 2015 at 7:46
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1$\begingroup$ They are different terms. arent they ? $\endgroup$– Bilal KhanSep 19, 2015 at 7:49
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2$\begingroup$ You're right. From one point of view, friction is a particular type of damping. That said, in more advanced contexts people say "friction" to mean "damping". $\endgroup$– DanielSankSep 19, 2015 at 7:52
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$\begingroup$ Damping, as in your link, usually refers to the $x'$ term in $mx''-bx'-kx=0$ (here, spring-mass-damper model). It refers to viscous friction, either caused by hydraulics or air resistance. Friction, on the other hand, is independent of velocity (Coulomb's law of friction) and most often refers to the resistance between two solids moving against each other (cars on the road, boxes on inclined planes, etc.). $\endgroup$– samlafJun 2, 2020 at 4:25
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2 Answers
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They are entirely different concepts. Your question is like asking "What is the difference between "temperature" and "weather"?" The term "damping" in physics typically refers to an effect that causes a reduction in the rate at which some process takes place. For the case of harmonic motion this can result in a reduction (over time) of the amplitude of a harmonic oscillation. "Friction" typically refers to a (dissipative) force acting on a system. Friction can be the cause of damping in a system.
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So there are different kinds of damping on simple harmonic oscillators, but the most common type is a force linearly proportional to velocity acting in the direction opposite to the direction of motion of the oscillator. This works for a vertically oriented spring with an object hanging at the end, since that single damping force is drag, which is a type of friction for objects moving in fluids, but for that same unit oriented horizontally on a surface, there is additional kinetic friction between the surfaces opposing the motion of the object. That means there are multiple distinct 'damping forces', one drag and one of kinetic friction, and so the usual model of a damped oscillator no longer works. In other words, different kinds of friction can be forms of damping.
answered Sep 19, 2015 at 5:37