The direction of three forces acting on a line has to be concurrent?

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SUMMARY

The discussion centers on the principle of concurrency in the context of three forces acting on a line. It is established that for a system to be in equilibrium, all three lines of action must intersect at a single point; otherwise, a net torque will occur. The participants reference a "simple" proof from a textbook that supports this conclusion, emphasizing the importance of understanding the geometric relationship between the forces.

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Jason Ko
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I found this theorem in D. Morin's book on mechanics. How to prove it mathematically? Does it have a name?
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Take the point of crossing of two of the force lines of action. If the third line of action does not pass through that crossing, there is a net torque and therefore this cannot happen for a system in equilibrium.
 
Thanks! I was being stupid
 
Jason Ko said:
Thanks! I was being stupid
Probably you didn't read the "simple" proof provided below the statement that you highlighted in the textbook.
 
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kuruman said:
Probably you didn't read the "simple" proof provided below the statement that you highlighted in the textbook.
Nor I. Good thing I agree with Morin though … 😛
 

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