The formula [Inline image 1] is valid for instaneous velocity and speed, but not average velocity and speed over an interval. I think that maybe that was the point of the example in the textbook.
Suppose we take 4 samples around the track. The average velocity is given by: Vavg = AVG([ 6.66, 0], [0, 6.66], [-6.66, 0], [0, -6.66]) = ([ 6.66, 0] + [0, 6.66] + [-6.66, 0] + [0, -6.66])/4 = [0, 0]/4 = [0, 0] However because speed has no direction (you cannot travel at -10km/h for example), the average speed is given by: Savg = AVG (6.66, 6.66, 6.66, 6.66) = 6.66 Of course, this distinction is secondary to the more important distinction that velocity is a vector (length and direction) while speed is a scalar (magnitude only). gray From: softimage-boun...@listproc.autodesk.com [mailto:softimage-boun...@listproc.autodesk.com] On Behalf Of Matt Lind Sent: Thursday, February 14, 2013 01:42 PM To: softimage@listproc.autodesk.com Subject: RE: Difference between a force and a velocity ? Like I said multiple times already. Take it up with the physicists and mathematicians. The example given is from a physics text book. You got a problem, take it up with the author. Sheesh! From: softimage-boun...@listproc.autodesk.com<mailto:softimage-boun...@listproc.autodesk.com> [mailto:softimage-boun...@listproc.autodesk.com] On Behalf Of Alok Gandhi Sent: Thursday, February 14, 2013 5:15 AM To: softimage@listproc.autodesk.com<mailto:softimage@listproc.autodesk.com> Subject: Re: Difference between a force and a velocity ? "If you have a problem with that, take it up with the physicists and mathematicians." Sorry Matt but I think you're wrong, and you can consider me a mathematician (I have a Masters in Mathematics and a Bachelor in Physics, Chemistry and Mathematics). Just taking a pure math approach now to set things right. Velocity is a vector as we know with a magnitude as Speed and a direction. So we can write: [Inline image 1] Where 's' is speed and 'v' is velocity and [Inline image 2] is the magnitude of the velocity. Now in the above equation, we cannot have 's' as non-zero and 'v' as zero. Because if 's' is zero , 'v' will be zero and if 's' is non-zero so will be 'v'. Here is a reference: http://bit.ly/XOAM50 Cheers ! Alok Gandhi Lead TD Modusfx
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