Re: Difference between a force and a velocity ?

[Alok]

Totally agree with you Graham, and that is why is my earlier post I had clearly mentioned the distinction between average and instantaneous velocities. Moreover, in case of CG we never talk of average velocities, it is always instantaneous. So the example of average velocity was not relevant. On 14/02/2013 2:57 PM, Grahame Fuller wrote: 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 ----- No virus found in this message. Checked by AVG - www.avg.com Version: 2012.0.2238 / Virus Database: 2639/5601 - Release Date: 02/13/13