Three identical spheres lie in contact with one another on a horizontal plane. A fourth(adsbygoogle = window.adsbygoogle || []).push({});

sphere rests on them, touching all three. Show that, in equilibrium, the coefficient of

friction between the spheres is at least (rad(3)-rad(2)) and that the coefficient between each sphere and the plane is at least (rad(3)-rad(2))/4

The only thing I can think to use here is summing forces. But woah, I am so stuck. Do I have the right idea even? Any help would be appreciated it!

Thanks!

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# Homework Help: Help with pool ball pyramid problem

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