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## Homework Statement

A cylinder having a mass of 2.0kg can rotate about its central axis through point O. Forces are applied as show: F1 = 6.0N, F2 = 4.0N, F3 = 2.0 N, and F4 = 5.0N. Also, r = 5.0cm and R = 12 cm. Find the (a) magnitude and (b) direction of the angular acceleration of the cylinder.

http://edugen.wiley.com/edugen/courses/crs1650/art/qb/qu/c10/fig10_42.gif

## Homework Equations

## The Attempt at a Solution

as of yet, i'm not looking for the solution to the entire problem, because i'm stuck on the first step of finding the net torque. this is what i have:

net torque = F1R - F2R - F3r + F4R = 6*0.12 - 4*0.12 - 2*0.05 + 0 = 0.14 N m

the book's solution for the net torque is 71 N m. i also got a similar problem wrong for presumably the same reason. the units are newtons and meters, and i'm sure my calculator works fine. what is going on here?