Ball mass m and radius r rolls down ramp with coefficient of static friction of mu. If the ball is released from rest what is the maximum angle theta of the ramp that the ball rolls without slipping?(adsbygoogle = window.adsbygoogle || []).push({});

I've got theta max = inverse(tan(mu)) but the answer in the book is

theta = inverse(tan(3.5mu))

I'm not sure where the 3.5 comes in could someone please explain?

Also if 2 balls roll down a ramp, one is filled with fluid the other not which one reaches the bottom first. The mass cancels out the the equation for the acceleration so it seems to me they should reach the bottom at the same time. Just wanted to verify that this is correct.

Thanks in advance

Carla

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# Rolling ball

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