This problem is due on my webassign homework in 3 hours and I can't get it right!!(adsbygoogle = window.adsbygoogle || []).push({});

Calculate the net torque about the axle of the wheel shown in Fig. 8-39. Assume that a friction torque of 0.43 mN opposes the motion and that F = 26.

The picture is here: http://www.webassign.net/giancoli/8-39alt.gif

What I did:

The 35 N force will move the wheel clockwise so the torque will be -

28 N force will move it counterclockwise so torque will be +

26 N force will move it clockwise so force will be -

They forces are all perpendicular to the radius so its just T = r X F

35 N force T = 35 N X .12 m = -4.2 (moves cw)

28 N force T = 28 X .24 m = 6.72 (moves ccw)

26 N force T = 26 X .24 m = -6.24 (moves cw)

So then including the friction torque which opposes the motion of .43 I put

6.72 - 4.2 - 6.24 - .43 = -4.15 is the net torque and because its - it movies in the clockwise direction

Web assign says -4.15 is WRONG! What am I doing wrong, please help!

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# Calculate the net torque about the axle of the wheel

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