# Homework Help: Simple question: unit vector

1. Jan 22, 2005

### Heart

Hi,

I'm wondering if anyone knows how to input a unit vector that lies between X and Y axes, into a Master Physics answering box.

One of the questions I'm working on required a unit vector (to point a direction) to be part of the answer. I know that the direction is between the X and Y axes so I tried using (sqrt0.5,sqrt0.5,0) as my unit vector but that didn't work out. It seems that they want the the unit vector in terms of x_unit, y_unit, z_unit (in mastering physics x_unit = x capped/x with a hat).

Any helps would be greatly appreciated.

2. Jan 22, 2005

### Heart

Should I try using x_unit*y_unit as my unit vector?

I know that x_unit, y_unit, z_unit represent unit vectors in x, y, z directions, respectively. I have only 2 more chances left.

Should I try this -k*(q_0)*(q_3)*y_unit*x_unit/(sqrt((d_2)^2+(d_2)^2))^2

(It's a force in an xy-plane.)

Last edited: Jan 22, 2005
3. Jan 22, 2005

### QuantumDefect

gah i hate mastering physics, i had to use it for Mechanics last semester :/

Usually its expressing the vector using it's components such as
w=((x_unit)^2+(y_unit)^2+(z_unit)^2)^1/2

Last edited: Jan 22, 2005
4. Jan 22, 2005

### Heart

After searching on the internet, I found that i_unit*j_unit = 0 so the answer in my previous reply is probably wrong. Anyone?

5. Jan 22, 2005

### Heart

So would the unit vector in an xy-planet = ((x_unit)^2+(y_unit)^2))^1/2? = (sqrt0.5, sqrt0.5, 0)?

But wouldn't that "w=((x_unit)^2+(y_unit)^2+(z_unit)^2)^1/2" be a scalar quantity? then isn't it no longer a vector and cannot act as a (unit) direction vector?

6. Jan 23, 2005

### Heart

OK, how about if I ask this. I want to write a unit vector that lies 45 deg. from either x/y axis, interm of unit vectors x_unit and y_unit, is it possible to do that?

7. Jan 23, 2005

### Heart

I figured it out, thanks for your help.