Thanks! So I'm trying to understand the concept of moments around an axis. I'm at a problem, and they ask to find a moment around the z-axis. There is a force in the J direction, and it says that that force pointing in the J direction has no contribution to the moment about the z-axis
Why is that? Is it because there is no Z component to the force?
@Axel: In general, whenever you get some weird-ass formula like $\tau = \vec{r} \times \vec{F}$, try to find a simple case so that you can get intuition.
Well, with the bike wheel, you have to push so that the force is not directed straight at the center of the weel.
Is anyone else having trouble logging into Meta? I'm logged in to the main site, and my other SE accounts automatically recognize me and log me in. But none of the Meta sites recognize me at all, even when I manually click on "log in."
lol - had almost finished an answer.... then another member got there just before me (so, as my answer would have been an unnecesary duplicate, I discarded what I had done)... gotta get faster with the math jax...
