# Homework Help: Vector 2B - Vector A (graphical method)

1. Sep 15, 2008

### s31t8n8

1. The problem statement, all variables and given/known data

Vector A is 4.00 units and 40* below x-axis. Vector B is 3.00 units and 25* below -x-axis. Use the graphical method (only ruler and protractor) to find Vector 2B - Vector A. I have to find the magnitude and direction.

When I did it I got 8.5 and East, but I'm not sure if I did it right. When they say 4.00 and 3.00 units, is that the ax component of the vector? That's the way I did it. I drew out the vector then measured 3 and 4 units on the ax comp. of both vectors, then measured from that point down to the vector and got the ay component. Then I just solved for the magnitude.

thanks

2. Sep 15, 2008

### LowlyPion

The vector length is 4 at an angle of 40 degrees down below positive X axis and the other vector is 3 long pointing down from the negative x-axis. (The other direction of x)

But they say 2*B which makes that vector 6 long.

3. Sep 15, 2008

### s31t8n8

ok i just redrew it and now im lost. im getting confused about what theyre asking

4. Sep 15, 2008

### LowlyPion

You've drawn the two vectors - doubling B?

Then reverse Vector A - same length - opposite direction.

They say 2*B - A right. This is vector subtraction. But you do that by "adding" the negative of the Vector A.

Now add these two vectors together.

5. Sep 15, 2008

### s31t8n8

ok i did it again and im sure i got it wrong again but i got
2*B-A= -.8i-.6j
magnitude = 1