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Ryker
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I'm just doing dynamics of rotational motion and was wondering if anyone could help me with the direction the friction points when you have a rope looped around a cylinder and it starts unwinding. The book says the force of friction does no work and is also responsible for the cylinder to actually turn. My first guess was that friction would point towards the centre of the cylinder, since it's undergoing circular motion and the acceleration would therefore have to be pointed there, but on the other hand it seems more intuitive that friction would point tangential to the circle. Or is it actually somewhere in between, because the cylinder's linear speed (of points at its rim) is increasing and isn't constant? Perhaps so that the normal force of the rope points towards the center of the cylinder and the friction tangentially to it, the resulting net force being somewhere in between?
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