Vector Displacement: Find Speed, Velocity, & Angle

AI Thread Summary
The discussion focuses on calculating total vector displacement, average speed, and average velocity for a motorist's journey with multiple directional changes. The motorist travels south, west, and northwest, prompting confusion about how to determine the angle of the total vector displacement. It is clarified that simply summing the magnitudes of the distances traveled does not yield the correct displacement, as displacement considers direction. To find the total displacement, one must add the vector displacements and then calculate the magnitude from that resultant vector. Understanding the distinction between total distance traveled and vector displacement is crucial for solving the problem accurately.
1PRFall2006
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Homework Statement


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.


Homework Equations


dX/dT
dV/dT


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.
 
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What is the total vector displacement? How did you find the magnitude?
 
all I had to do is add up the magnitudes of the vectors. I don't need the angle to find the magnitude.
 
1PRFall2006 said:
all I had to do is add up the magnitudes of the vectors.

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 traveled 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.
 
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