How is Average Velocity Calculated for a Two-Part Journey?

AI Thread Summary
To calculate average velocity for a two-part journey, total displacement must be determined by vectorially adding the displacement vectors from each segment of the trip. The first leg of the journey involves traveling east at 73 km/h for 1.4 hours, while the second leg is at 129 km/h at an angle of 30° east of north for 0.5 hours. The average speed for the entire trip is calculated to be 87.7 km/h. The average velocity requires finding the x and y components of each displacement, summing them, and then using trigonometry to determine the resultant magnitude and direction. Proper calculations will yield the correct average velocity magnitude and direction.
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A car travels east at 73 km/h for 1.4 h. It then travels 30.0° east of north at 129 km/h for 0.5 h.
(a) What is the average speed for the trip?
87.7 km/h

(b) What is the average velocity for the trip?
Magnitude ____ km/h
Direction ____



Homework Equations


V avg= delta r/delta t
delta r= rf-ri/tf-ti


The Attempt at a Solution



64.5km-102.2km=-37.8km
.5h-1.4h=-.9h

(-37.8km)/(-.9h)=42.1 km/h

not sure how to find the direction, but I am doing my h.w. online and it tells me my answer is incorrect. Am I even going in the right direction?
Any help please?
 
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Average velocity is total displacement divided by total time. You have to get the total displacement by vectorially adding up the 2 displacement vectors.
 
so Jay you are saying I have to find the x and y comp to find the total displacement
 
Yes, get the x and y components of each of the 2 displacements you have calculated, add up each separately, then get the resultant displacement magnitude and direction using pythagorus and trig. That's the total displacement, you have the time, solve for the average velocity magnitude and direction.
 
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