Find two unit vectors that are parallel to the xy plane

In summary, the question asks for two unit vectors that are parallel to the xy plane and perpendicular to the vector [1,-2,2]. This can be achieved by finding a vector of the form [a, b, 0] and taking multiples of it. The two possible solutions are [2, 1, 0] and [4, 2, 0], both of which are unit vectors.
  • #1
PiRsq
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I got the answer to this question but I don't quite understand why its like that...The question is:

Find two unit vectors that are parallel to the xy plane and perpendicular to the vector [1,-2,2]
 
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  • #2
Find two unit vectors that are parallel to the xy plane and perpendicular to the vector [1,-2,2].

It would be better to show us what you had done and exactly what it is that you "dont quite understand".

However, since this is very simple: Saying that a vector is "parallel to the xy plane" means that its z component i 0- you are looking for a vector of the form [a, b, 0].

Saying that the vector is "perpendicular to the vector [1, -2, 2] means that its dot product with that vector is 0: [a, b, 0].[1, -2, 2]= a- 2b= 0.

That is one equation in 2 unknowns so it have an infinite number of solutions. In particular, if you take b= 1, then a-2= 0 so a= 2.
[2, 1, 0] is a vector "parallel to the xy plane and perpendicular to the vector [1, -2, 2]". Taking b= 2, a- 4= 0 so [4, 2, 0] is another. In fact, it is just [1, -2, 0] multiplied by 2. Obviously, if one vector is "parallel to the xy plane and perpendicular to the vector [1, -2, 2]", then any multiple of it is also because it is in the same direction.
 
  • #3
Plus, it says 'unit vectors'. So there's only 2 answers to this.
 

1. How do you find unit vectors that are parallel to the xy plane?

To find unit vectors that are parallel to the xy plane, you can simply use the i and j unit vectors, which lie on the x-axis and y-axis respectively. These two unit vectors are already parallel to the xy plane.

2. Can any two unit vectors be parallel to the xy plane?

Yes, any two unit vectors that are perpendicular to each other will be parallel to the xy plane. This means that as long as the i and j unit vectors are not in the same direction, they can form a pair of unit vectors that are parallel to the xy plane.

3. How do you determine the direction of the unit vectors parallel to the xy plane?

The direction of the unit vectors parallel to the xy plane is determined by the orientation of the x-axis and y-axis. The i unit vector points in the positive direction of the x-axis, while the j unit vector points in the positive direction of the y-axis.

4. Can unit vectors parallel to the xy plane have different magnitudes?

Yes, unit vectors parallel to the xy plane can have different magnitudes. The magnitude of a unit vector only indicates the direction it is pointing in, not its length. As long as the unit vector is perpendicular to the xy plane, it is still considered to be parallel to it.

5. How can you use unit vectors parallel to the xy plane in calculations?

Unit vectors parallel to the xy plane can be used in vector operations such as addition, subtraction, and scalar multiplication. They can also be used to represent the direction of a vector in the xy plane by multiplying them by the magnitude of the vector.

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