Physics puzzle
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 22nd September 2007, 04:32 AM #1 star882   diyAudio Member     Join Date: Mar 2007 Physics puzzle There is a circular running track 168 feet in diameter. Peggy Liska runs 10 laps around the track in 6 minutes. What is her average velocity in meters per second? Hint: Circumference is equal to diameter times pi. One meter is about 3.28 feet. One minute is 60 seconds.
 22nd September 2007, 06:51 AM #2 Nanook   diyAudio Member     Join Date: Feb 2004 Location: Chinook Country.Alberta zero... velocity is a vector and as such follows rules of vector addition. The net displacement from the origin is the distance travelled, therefore 0 distance travelled results in a 0 velocity. now average speed (which is a scalar) is (10 X 3.1416 X 51.3 metres)/(6mins X60 secs/min)=4.4686 metres/sec and is independent of the net displacement from the origin (think of it like a speedometer) so no puzzle here __________________ stew ☮ -"A sane man in an insane world appears insane." Let's help Ruth and Dave
planet10
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Location: Victoria, BC, NA, Sol III
Re: Physics puzzle

Quote:
 Originally posted by star882 There is a circular running track 168 feet in diameter. Peggy Liska runs 10 laps around the track in 6 minutes. What is her average velocity in meters per second?
168' = 51.2064 m
perimter = 160.86965 m
10 laps = 1608.6965 m
1608.7/360 sec = 4.4686 m/s is her speed...

but (just asking the question one knows there has to be a but...) end - start = 0 (because it is a circular track and she traveled an integer number of laps start = end) so avaege velocity is 0m/s

dave
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 22nd September 2007, 07:48 AM #4 planet10   frugal-phile(tm) diyAudio Moderator     Join Date: Oct 2001 Location: Victoria, BC, NA, Sol III Stew, t may seem i posted way after you, but ibecause of the way i browse the forum, i did not see your answer ... honest. (i go thru the list of new posts and open them in tabs and then slowly go thru them0 dave __________________ community sites t-linespeakers.org, frugal-horn.com, frugal-phile.com ........ commercial site planet10-HiFi p10-hifi forum here at diyA
 22nd September 2007, 08:29 AM #5 pinkmouse   diyAudio Moderator     Join Date: Apr 2002 Location: Rotherham, England But would she take off? __________________ Rick: Oh Cliff / Sometimes it must be difficult not to feel as if / You really are a cliff / when fascists keep trying to push you over it! / Are they the lemmings / Or are you, Cliff? / Or are you Cliff?
Geek
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Join Date: Sep 2004
Quote:
 Originally posted by pinkmouse But would she take off?
What did she take off?

 22nd September 2007, 09:15 AM #7 Nanook   diyAudio Member     Join Date: Feb 2004 Location: Chinook Country.Alberta np Dave... the thing here is that it must be understood the difference between a vector (like velocity) and a scalar (like speed). Of course some really interesting things happen when you do vector calculus...and end up with a scalar for those that may not know the difference: A vector has direction and magnitude, while a scalar does not (say like temperature or speed). scalar addition behave like normal "math", vector addition is the sum of all magnitudes and all directions... Vector or "triangular" addition is unique to vectors. so Dave, the average velocity is zero, while the average speed is 4.4686 m/s __________________ stew ☮ -"A sane man in an insane world appears insane." Let's help Ruth and Dave
pinkmouse
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Join Date: Apr 2002
Location: Rotherham, England
Quote:
 Originally posted by Geek What did she take off?
Sorry, I'll clarify - would she get airborne.
__________________
Rick: Oh Cliff / Sometimes it must be difficult not to feel as if / You really are a cliff / when fascists keep trying to push you over it! / Are they the lemmings / Or are you, Cliff? / Or are you Cliff?

 22nd September 2007, 09:25 AM #9 Nordic   diyAudio Member     Join Date: Sep 2005 But, does it blend?
 23rd September 2007, 01:33 AM #10 Nanook   diyAudio Member     Join Date: Feb 2004 Location: Chinook Country.Alberta airborne and blending? Pinkmouse:well if she was a huge mass and expelled or "voided' a large percentage of her mass long enough to create momentum (essentially the burn rate to rocket scientists), then she would. Her momentum would have to overcome the earth's gravitational field Nordic: scalars and vectors don't "blend". you can operate on scalars using vector calculus, the end result would be a vector field. That's what a "gradient" is , a vector field showing the change in scalars, with respect to a displacement (a vector) a nice explaination is here __________________ stew ☮ -"A sane man in an insane world appears insane." Let's help Ruth and Dave

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