A hollow, spherical shell with mass 1.95 rolls without slipping down a slope angled at 30.0. Find the minimum coefficient of friction needed to prevent slipping.(adsbygoogle = window.adsbygoogle || []).push({});

I have already calculated the acceleration of the sphere and the magnitude of the friction force on the sphere in previous parts. I used torque and newton's laws to find the acceleration and friction. They are:

a = 2.94 m/s^2

f = 3.82 N

I used the following equation for the sum of forces in the x-direction, which I oriented along the slope of the incline, with the positive direction down the incline. I didn't think I needed to use torque here, because I got the same answer that way as well.

(sum)Fx = mgsin(theta) - f = ma

= mgsin(theta) - (mu)mgsin(theta) = ma

mu = [a - gsin(theta)] / [-gsin(theta)]

mu = (-1.96 m/s^2) / (-4.9 m/s^2)

= 0.4

This coefficient of friction isn't right, but I'm sure I included all of the forces. Anyone know where I messed up? Thanks.

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# Homework Help: Minimum coefficient of friction to prevent slipping - torque

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