Cross Product Help: Homework Statement

  • Thread starter Thread starter TheRedDevil18
  • Start date Start date
  • Tags Tags
    Cross
AI Thread Summary
To find the vector product A × B for vectors A = 4i + 7j and B = 5i - 2j, the correct answer is -43k. The initial assumption that the z component was zero led to confusion, but the answer should be expressed simply as -43k without the i and j components. The online assignment system may not accept the full vector notation, causing frustration for users. This issue highlights the importance of understanding how answers are formatted in online systems.
TheRedDevil18
Messages
406
Reaction score
2

Homework Statement



Given two vectors A⃗ = 4i + 7j and B⃗ = 5i − 2j , find the vector product A⃗ × B⃗ (expressed in unit vectors).
Express your answer in terms of the unit vectors i, j, and k.

Homework Equations





The Attempt at a Solution



I know how to cross and multiply them but they don't give the z component so I assumed it was zero

This is what I got

0i + 0j - 43k

Why is that wrong ?, I'm doing this online assignment and it keeps telling me, "The correct answer does not depend on i,j and k"
 
Physics news on Phys.org
TheRedDevil18 said:

Homework Statement



Given two vectors A⃗ = 4i + 7j and B⃗ = 5i − 2j , find the vector product A⃗ × B⃗ (expressed in unit vectors).
Express your answer in terms of the unit vectors i, j, and k.

Homework Equations





The Attempt at a Solution



I know how to cross and multiply them but they don't give the z component so I assumed it was zero

This is what I got

0i + 0j - 43k

Why is that wrong ?, I'm doing this online assignment and it keeps telling me, "The correct answer does not depend on i,j and k"
You did it right. They probably just want -43k.

Chet
 
Chestermiller said:
You did it right. They probably just want -43k.

Chet

Yeah, I guess they just wanted -43k with the hat on top. Stupid system, now I lost 3% for each "wrong" attempt :mad:

Thanks for your reply
 

Thread 'Finding the number of ways to arrange identical balls in a circle (3 different colors)'

I tried to combine those 2 formulas but it didn't work. I tried using another case where there are 2 red balls and 2 blue balls only so when combining the formula I got ##\frac{(4-1)!}{2!2!}=\frac{3}{2}## which does not make sense. Is there any formula to calculate cyclic permutation of identical objects or I have to do it by listing all the possibilities? Thanks
View full post »

Thread 'Greatest possible value of a constant in polynomial'

Since ##px^9+q## is the factor, then ##x^9=\frac{-q}{p}## will be one of the roots. Let ##f(x)=27x^{18}+bx^9+70##, then: $$27\left(\frac{-q}{p}\right)^2+b\left(\frac{-q}{p}\right)+70=0$$ $$b=27 \frac{q}{p}+70 \frac{p}{q}$$ $$b=\frac{27q^2+70p^2}{pq}$$ From this expression, it looks like there is no greatest value of ##b## because increasing the value of ##p## and ##q## will also increase the value of ##b##. How to find the greatest value of ##b##? Thanks
View full post »

Similar threads

B Confusion about the angle between two vectors in a cross product
Replies
7
Views
3K
Dot Products With Orthogonal Vectors
Replies
4
Views
2K
Why does the cross product of two direction vectors....
Replies
2
Views
2K
How to solve for the general solution in a vector linear relationship?
Replies
8
Views
2K
How Do You Determine the Components of a Vector Perpendicular to Another?
Replies
1
Views
3K
Obtain an equation of the plane in the form ##px+qy+rz=d##
Replies
5
Views
1K
Vector of shortest distance between two skew lines
Replies
11
Views
3K
I with this question about vectors
2
Replies
63
Views
6K
Vectors: Proving the value of a•(b x c)
Replies
21
Views
8K
Line of intersection of two planes
Replies
9
Views
3K

Hot Threads

Recent Insights

Back
Top