0
$\begingroup$

I couldn't figure out the direction of this specific cross product example because of the angle. I tried the right hand rule several times but I can't seem to get it right. How did the direction turn out to be like this? And how should I shape my hand?

enter image description here

Improve this question
$\endgroup$
8
  • 2
    $\begingroup$ If you’re having a problem visualizing the right-hand-rule for $\vec{F_1}\times\vec{F_2}$ because you have to put your right hand into an awkward position, try it for $\vec{F_2}\times\vec{F_1}$, which is in the opposite direction. Or use your left hand and reverse the result. $\endgroup$
    – G. Smith
    Dec 5, 2019 at 16:59
  • $\begingroup$ As far as it seems to me that $F_2$ is coming out of the paper (in z-direction) and not in $xy$ plane. $\endgroup$
    – user240696
    Dec 5, 2019 at 17:38
  • $\begingroup$ @Knight Out of the paper but not in the $z$-direction. Look at the indicated angle of 120 degrees with the $x$-axis. $\endgroup$
    – G. Smith
    Dec 5, 2019 at 17:43
  • 1
    $\begingroup$ I've added the homework-and-exercises tag. In the future, please add this tag to this type of problem. This is one of the things that we ask you to do in our homework policy: physics.meta.stackexchange.com/questions/714/… $\endgroup$
    – user4552
    Dec 5, 2019 at 21:58
  • 1
    $\begingroup$ Please reference the source of this homework question. This is one of the things that we ask you to do in our homework policy: physics.meta.stackexchange.com/questions/714/… $\endgroup$
    – user4552
    Dec 5, 2019 at 21:58

1 Answer 1

Reset to default
-1
$\begingroup$

I like the following configuration

RHRule

To get $\vec{a} \times \vec{b}$ make your fingers sweep from one vector to the other, as if you are rotating $\vec{a}$ to meet $\vec{b}$ (dashed arrow below).

The cross product direction is where your thumb points.

In your question specifically, put the base of the fingers at $\vec{F}_1$ and the tips of the fingers at $\vec{F}_2$.

Answer

Improve this answer
$\endgroup$
1
  • $\begingroup$ Why the downvote without comment? $\endgroup$
    – John Alexiou
    Dec 6, 2019 at 22:23

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge that you have read and understand our privacy policy and code of conduct.

Not the answer you're looking for? Browse other questions tagged or ask your own question.