A quick question about scalar product of vectors...


by TA1068
Tags: product, scalar, vectors
TA1068
TA1068 is offline
#1
Apr14-08, 03:09 PM
P: 13
Attached is a .jpg of my problem.

I know how to find the scalar product of B*C (I think... 5, right?), but I don't really know where the 2 and 3 come into play. I've tried multiplying the values of C by 3 and then finding the scalar product, then multiplying the quantity by two, but that was incorrect.


I couldn't find it in my physics text. I guess it's probably something I should know, but I don't, so that's why I'm here! Any help would be greatly appreciated.
Attached Thumbnails
Vector Q.jpg  
Phys.Org News Partner Mathematics news on Phys.org
Researchers help Boston Marathon organizers plan for 2014 race
'Math detective' analyzes odds for suspicious lottery wins
Pseudo-mathematics and financial charlatanism
mathman
mathman is offline
#2
Apr14-08, 04:39 PM
Sci Advisor
P: 5,935
Your attachment couldn't be displayed. Try something else.
TA1068
TA1068 is offline
#3
Apr14-08, 04:41 PM
P: 13
Oops! Here it is:

img87.imageshack.us/img87/2452/vectorqqp8.jpg

Pere Callahan
Pere Callahan is offline
#4
Apr14-08, 06:32 PM
P: 588

A quick question about scalar product of vectors...


Quote Quote by TA1068 View Post

I know how to find the scalar product of B*C (I think... 5, right?), but I don't really know where the 2 and 3 come into play. I've tried multiplying the values of C by 3 and then finding the scalar product, then multiplying the quantity by two, but that was incorrect.
Well this was correct. Unless you made a mistake in carrying out the calculations ...
Remember when you multiply the vector C by the number 3 you have to multiply each component of C by this number 3, giving you

3C = 3(-1,-1,2)=(-3,-3,6)

I suggest double-checking your calculations and if this doesn't help....show us what you have done and we can most likely find your mistake.


For the scalar product of B and C, five is correct.

B.C = (-3,0,1).(-1,-1,2)=3+0+2=5, well done.
TA1068
TA1068 is offline
#5
Apr14-08, 07:56 PM
P: 13
So for my work...

B = (-3, 0, 1) and
C = (-3, -3, 6)

So... 9 + 0 + 6 = 15
15 * 2 = 30

...I could have sworn thats what I was doing all along, but for some reason I kept getting 60 for my answer. Hmm.

Anyways, thanks greatly for any and all help!
Pere Callahan
Pere Callahan is offline
#6
Apr14-08, 07:58 PM
P: 588
So are you content with 30 now? It seems corect to me.


Register to reply

Related Discussions
Question about Scalar Product of Vectors General Math 20
vectors: cross product question Calculus & Beyond Homework 4
Scalar product to find angle between two vectors Introductory Physics Homework 7
scalar product question Introductory Physics Homework 12