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PeterO
#4
Sep25-11, 06:37 PM
HW Helper
P: 2,316
Difference between Average Speed & Average Velocity in Velocity-Time graphs?

Quote Quote by rayj098 View Post
Most of it. So lets say I had these two graphs:






How would I find distance traveled, displacement, speed and velocity from these graphs?


I would appreciate it if you could show your work.


Thanks in advance.
You start by drawing vertical lines from each of the corners of the graph - where you have drawn dots/plotted points.

In the first case this divides the whole thing into a series of triangles and rectangles, which are easy to find the area of.

In Part 1 Sections A,B & C are above the time axis, so represent positive areas for displacement.
Sections D, E & F are below the axis, so represent negative areas for displacement.

Lets pretend the areas under A,B&C was 200, and the Areas fro section D,E&F was -300

That would represent a total displacement of -300, but a distance covered of 500

Since the time was 720 seconds, that would mean average velocity = -100/720 while the average speed would be 500/720

Similar working for part 2 except you have to estimate some areas as the bounding line in some cases is a curve.
If you know the equation of the curve, you could use integration but in physics we usually use either a "counting the squares" technique, or approximate to triangles/rectangles.