Calculate Torque of 24 cm Wheel in XY Plane w/ Force (-35i + 39j) N

[hxs6]

A wheel of diameter 24.0 cm is constrained to rotate in the xy plane, about the z axis, which passes through its center. A force F = (-35.0 i + 39.0 j) N acts at a point on the edge of the wheel that lies exactly on the x-axis at a particular instant. What is the torque about the rotation axis at this instant?

i already got T=0i+0j mN which i still don't exactly know why, but i can't figure out what k is.

 

[arildno]

Eeh??
Your answer is wrong in so much.
Do you know about the cross-product definition of the torque?

 

[cristo]

1. What is the position vector of the point at which the force is being applied?
2. What is the definition of torque?

If you can answer these two points, then you can answer your question.