Cross product and Dot product problem

From there, you can use the fact that |v x w| = |v| |w| sinθ to find sinθ, and then take the inverse tangent to find θ. So your final answer would be "In summary, you can find the tan(θ) between two vectors v and w by finding the magnitude of their cross product, using that to find sinθ, and then taking the inverse tangent of that value."
  • #1
PsychonautQQ
784
10

Homework Statement



if v x w = <5,5,-2>
(v cross w)

and

v * w = 6
(v dot w)

then what is the tan(θ) between the two vectors v and w?


The Attempt at a Solution



well I was thinking v x w = |v||w|sinθ
as well as v dot w (v*w) = |v|w|cosθ

divide one equation by the other and the absolute values on the right cancel out,
but then you get a vector divided by a number on the left side equals tanθ

is this how you do this problem?
 
Physics news on Phys.org
  • #2
You have a problem with the first equation in your attempt at solution. It should read:
|v × w| = |v| |w| sinθ

You are right that v × w is a vector, and the correct equation for it would be:
v × w = |v| |w| sinθ n
where n is the unit vector perpendicular to both v and w given by the right-hand rule.
 
  • #3
To expand on what Jolb said, since you're given that v x w = <5, 5, -2>, you have enough information to find |v x w|.
 

What is the difference between cross product and dot product?

The cross product and dot product are both mathematical operations that involve two vectors. The main difference between them is that the dot product results in a scalar (a single number), while the cross product results in a vector (a quantity with both magnitude and direction).

How do I calculate the dot product of two vectors?

The dot product can be calculated by taking the product of the corresponding components of the two vectors and then adding them together. For example, if vector A is (2, 4, 3) and vector B is (5, 1, 2), the dot product would be (2 * 5) + (4 * 1) + (3 * 2) = 10 + 4 + 6 = 20.

What is the cross product used for?

The cross product is used to find a vector that is perpendicular to two given vectors. It is also used in physics and engineering to calculate torque and angular momentum.

How do I calculate the cross product of two vectors?

The cross product can be calculated by taking the determinant of a 3x3 matrix, with the first row being the unit vectors i, j, and k, the second row being the components of the first vector, and the third row being the components of the second vector. The resulting vector will have a magnitude equal to the area of the parallelogram formed by the two vectors and a direction perpendicular to both of them.

Can the dot product or cross product be negative?

Yes, both the dot product and cross product can be negative. The sign of the dot product depends on the angle between the two vectors, while the sign of the cross product depends on the direction of the resulting vector.

Similar threads

  • Calculus and Beyond Homework Help
Replies
13
Views
2K
  • Calculus and Beyond Homework Help
Replies
2
Views
1K
  • Calculus and Beyond Homework Help
Replies
5
Views
1K
  • Calculus and Beyond Homework Help
Replies
4
Views
1K
  • Special and General Relativity
Replies
4
Views
788
  • Calculus and Beyond Homework Help
Replies
5
Views
2K
  • Calculus and Beyond Homework Help
Replies
1
Views
6K
  • Calculus and Beyond Homework Help
Replies
4
Views
885
  • Calculus and Beyond Homework Help
Replies
1
Views
1K
  • Calculus and Beyond Homework Help
Replies
1
Views
1K
Back
Top