Find the net torque about an axis through O

[jesuslovesu]

http://img334.imageshack.us/img334/6018/omg8gp.th.png

Find the net torque about an axis through O

I know Torque = F*r*sin(angle) but how the heck am I supposed to get the radius for that?

 

[andrewchang]

if the force is going through O, and you set the axis of rotation at O, then there is no net torque. (the radius is zero)

 

[mukundpa]

r*sin(angle) is the perpendicular distance of the force vector from the axis of rotation.

 

[vaishakh]

Please provide me a magnifying lens, my specs don't help me much!
Anyway, for beginners write the force in vector form as well as the vector r which is the vector joining the point with respect to which torque is measured to the point at which force is applied. Here the torque is defined as the croos product of vector r to vector f

 

[mukundpa]

beware! don't give pressur to your eyes. r is zero here. you can't see it.

 

[Astronuc]

if the force is going through O, and you set the axis of rotation at O, then there is no net torque. (the radius is zero)

Yeah, from the diagram given, it looks as though the force is applied at O, so there is no net torque.

 

[andrewchang]

trick question, i guess? if i were taking a test and i saw that, i wouldn't be too happy. =P