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When I ask students to calculate the magnitude of the average velocityfor a
simple projectile problem (e.g., ball thrown horizontally from a roof),they
often simply add the initial and final speeds and divide by 2. . .
. . . 2) Why
is the quantity they are calculating not even the correct average speed?
doubt think, "when acceleration is constant (as it is in projectilemotion),
this is how you can calculate average velocity (in one dimension); andspeed
is the magnitude of velocity, right?"work?
Does anyone have a good brief intuitive explanation (for beginning
calculus-based-physics students) of the reason(s) that this doesn't
(or maybe a reference to a particularly good textbook explanation)[Since this is somewhat related to the current discussion entitled
I suppose this is a two-part problem: 1) Why is the average of the
magnitude of a vector not the same as the magnitude of the average? >
"Problem", which I haven't been following in complete detail, I hopethis
request doesn't duplicate something that was just covered there.]
_____________________________
Fred Lemmerhirt
Waubonsee Community College
Sugar Grove, Illinois
flemmerhirt@mail.wcc.cc.il.us
http://chat.wcc.cc.il.us/~flemmerh/physics.html