Answers

2016-03-01T15:54:26+05:30
friction opposes the direction of the velocity, but the problem is when I don't know what the direction of the velocity is. When I'm drawing a FBD for complex systems with ramps and pullies and stuff (with angular forces considered), I don't really know if the mass is accelerating/moving down or up and hence I don't know if the friction is to the left or to the right.
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