Register to reply 
Clear up some cross product confusion for me 
Share this thread: 
#1
Feb1912, 01:34 PM

P: 132

Here is what I have
A=xro+yr1 B=yro+xr1 I need to find A x B I am confused about do it because The components of A and B are in terms of vectors If A = 3i + 4j + 7k and B = 2i + 2j + 1k I would have no problem (these numbers are meaningless just giving an example) finding A x B but I don't have components I have vectors. Can some one explain how to do this. Thanks 


#2
Feb1912, 01:47 PM

P: 132

Could I set it up as follows
Sorry I don't no how to input a matrix hopefully this can get the idea across ro r1 k ro r1 x y 0 x y y x 0 y x and then do the normal cross product thing where you multiply diagonals and so on. The thing that troubles me is there is really no k component. The only thing I know is my answer will be perpindicular to the plane with r0 and r1 so not sure what to do 


#3
Feb2012, 04:10 PM

Sci Advisor
P: 6,106

AXB = (x^{2}  y^{2})r0Xr1.
I am assuming x and y are scalars. 


#4
Feb2012, 04:28 PM

Sci Advisor
HW Helper
Thanks
P: 26,148

Clear up some cross product confusion for me
hi 2slowtogofast!
what are ro x ro and r1 x r1 ? 


#5
Feb2012, 08:08 PM

P: 132

@tinytim
roxro = 0 I can see how that will simplify things I am confused about the distributive law part A x (B+D) = (AxB)+(AxD) I have somthing more like this (xro+yr1) x (yro+xr1) = (xro+yr1) x yro + (xro+yr1) x xr1 Use the distributive rule again on the RHS (xro x yro) + (yr1 x yro) + (xro x xr1) + (yr1 x r1) Then the first and last terms are 0. Am on the right track or did I make a wrong turn somewhere 


#6
Feb2112, 04:44 AM

Sci Advisor
HW Helper
Thanks
P: 26,148

hi 2slowtogofast!
(just got up ) now what is the relationship between r1 x ro and ro x r1 ? 


#7
Feb2112, 06:12 PM

P: 132

r0 x r1 = (r1 x r0)
If that is correct i think i can take it from there thanks for the help 


Register to reply 
Related Discussions  
Cross Product Confusion  Calculus  5  
Logic confusion  formally clear but practically not so.  Set Theory, Logic, Probability, Statistics  7  
Angle between 2 vectors using 1) Dot product and 2) cross product gives diff. answer?  Calculus & Beyond Homework  8  
Quick question to clear up some confusion on Riemann tensor and contraction  Special & General Relativity  3  
Need to clear confusion on a simple lense problem (solution is worked out )  Introductory Physics Homework  2 