What is the net torque about the axle?

[a.a]

Homework Statement

The 19.6 cm diameter disk rotates on an axle through its center. F1=22.8 N, F2=32.5 N, F3=32.5 N, F4=22.8 N, and d=4.60 cm. What is the net torque about the axle?

Homework Equations

Torque = F r sin (angle)
F = m g

The Attempt at a Solution

I found all the torques acting on the center, disregarded T1 because its sort of passing through the center and isn't really shown on the diagram.

T1 = 0
T2= (32.5)(0.196) = 6.37 Nm
T3= -(32.5)(sin 45)(0.046)= -1.057 Nm (counterclockwise)
T4= (22.8)(0.046)= -1.0488 (counterclockwise)

Tnet = 4.26 Nm

This isn't the right answer, can someone please help and explain where I am going wrong..

 

[Hootenanny]

For a standard coordinate axis, counter-clockwise is usually taken as positive.

 

[xboy]

Re-check the calculation for T2 .

 

[Hootenanny]

Re-check the calculation for T2 .

T2 looks fine to me (with the exception of the sign minus of course).

 

[xboy]

Shouldn't he multiply the force with the radius (as opposed to the diameter)?

 

[Hootenanny]

Shouldn't he multiply the force with the radius (as opposed to the diameter)?

Of course he should. And I should pay more attention

 

[a.a]

Of course he should. And I should pay more attention

wow.. thanks.. that was a dumb mistake...