Diagram: http://snipurl.com/c8h6 [Broken](adsbygoogle = window.adsbygoogle || []).push({});

A spool of wire is unwound with a constant force F. The spool is a solid cylinder mass M, radius R, and doesn't slip.

Show the acceleration of the centre of mass is 4F/3M.

what i have done:

[tex] \sum Torque = I\frac{a}{R}[/tex]

[tex] FR=I\frac{a}{R} [/tex]

[tex] \frac{FR^2}{I}=a[/tex]

Now, for I, I used the parallel axis theorem and got

[tex]I=\frac{1}{2}MR^2+ MR^2 = \frac{3}{2}MR^2[/tex]

but plugging into my formula above yields [tex]a=\frac{2F}{3M}[/tex]

how do i get a=4F/3M????

thanks for your help

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# Homework Help: Spool of wire

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