Vectors help? How do I find a constant of this vector?

[xllx]

The vector is this:

V=(5i-j)+q(i+4j) and it is in the direction of north-east.

I have to find the constant (q) of this vector. The part of the question before this showed that if a vector of ki+kj, where k was a positive constant is a vector of magnitude k(square root)2. So I don't know whether I have to use that in part of this answer.

I really have no idea where to start or what to do because I don't know what V is. But I was thinking about the direction, so do I have to adjust the q so that the angle is 45 degrees?

Any help at all would be greatly appreciated. Thanks.

 

[LowlyPion]

Welcome to PF.

First I think you would want to rearrange the coefficients wouldn't you?

V = (5+q) i + (4q - 1) j

Next they tell you that the direction is Northeast.

That suggests that the coefficients of i and j are equal doesn't it?

So ...

If you wanted to find |V| (magnitude of V) then you would use what they showed with the k i + k j example.

 

[xllx]

Thankyou so much!

So from that, I've managed to get q= 2.

(5+q)i = (4q-1)j
6=3q
q=2

Is this right?
Thanks again!

 

[LowlyPion]

Thankyou so much!

So from that, I've managed to get q= 2.

(5+q)i = (4q-1)j
6=3q
q=2

Is this right?
Thanks again!

Looks right to me.