Physics QBank #95

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Physics QBank #95

Post by avo » Mon Jul 22, 2019 4:47 pm

Hi! For this question, I had approached it using the center of mass equation, but noticed the explanation for this question involved using torque instead. Is that the preferred method for these kinds of questions? Or does either method work? Thanks!
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Re: Physics QBank #95

Post by NS_Tutor_Mathias » Mon Jul 22, 2019 6:07 pm

Those are very much the same thing in this scenario. If you solve such that the center mass would be in the middle, it would naturally be in equilibrium.

You can think of it as either:
1. Finding the center mass of the entire "left" system and the center mass of the entire "right system"


2. Doing more or less the same thing, but then pretending that these masses are acting on massless levers around the pivot.

Or to be totally honest, you can think of it whatever way you like. There are many, many more ways to look at this and solve these. The torque approach has the advantage that it would let you solve angled situations more easily (what if I wanted to balance this meter stick at a 30 degree angle to the horizon?). Overall this is a connection worth making though: Both torque and center mass are specific case studies of how forces act on things, and indeed having an off-center center of mass will cause an object resting on a pivot to rotate - in other words, experience torque.

Take this as a very good sign: You saw a problem and you fashioned yourself a solution to it. And you created exactly the kind of solution pathway that took into account the problem you were facing!
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