# Torque r & F two angles

1. Nov 12, 2006

### Ronnin

Unless r and F are perpendicular, there are always two angles between their directions that give the same torque for given magnitudes of r and F. Explain why?

Perhaps I cannot visualize the question, but I cannot see how this can be. As the force moves to the perpendicular position the torque increases. Am I missing something?

2. Nov 12, 2006

### neutrino

Use the definition of torque. If one angle between the p.v and force vector is theta, what about the other?

Edit: I guess this holds only for the magnitude of the torque.

Last edited: Nov 12, 2006
3. Nov 12, 2006

$$\tau = rF \sin \theta$$

$$sin \theta = \sin (\pi - \theta)$$​

4. Nov 12, 2006

### Ronnin

I guess I figured that would put the angle outside of between the two angles.