Vector displacement

1. Sep 23, 2007

1PRFall2006

1. The problem statement, all variables and given/known data
A motorist drives south at 28.0 m/s for 3.00 min, then turns west and travels at 25.0 m/s for 2.00 min, and finally travels northwest at 30.0 m/s for 1.00 min. For this 6.00 min trip, find the following values: Total vector displacement, average speed, and average velocity.

2. Relevant equations
dX/dT
dV/dT

3. The attempt at a solution
I can find the average speed and average velocity. I can also get the magnitude of the total vector displacement. The problem I'm having is the angle. I don't even know who to approach this problem to find the angle.

2. Sep 23, 2007

learningphysics

What is the total vector displacement? How did you find the magnitude?

3. Sep 23, 2007

1PRFall2006

all I had to do is add up the magnitudes of the vectors. I don't need the angle to find the magnitude.

4. Sep 23, 2007

learningphysics

That's not right. That gives the total distance travelled... That's not the same as the magnitude of the total displacement...

Suppose I travel 40m east, then 20m west. The total distance travelled is 60m. The displacement is 20m east... ie the magnitude of the total displacement is 20m.

You need to find the total displacement... ie add up the vector displacements... then at the end... find the magnitude of that.