Originally posted by tafnut
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Gonna be a scorcher in Austin today
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Originally posted by bekeselassieNo doubt temperature affects longer distances, but the 1500? I don't know for sure, but here's something to consider. Even if the race distance doesn't seem to come into play so much in the heat, how about the warmups plus the race? For an 800 or mile my typical warmup was a mileandahalf before my accelerations and such. It took that much before I really felt everything was flowing just right.
In late spring, I'd step to the starting line already dripping sweat sometimes. So could it be argued that if we include the warmups then not only the 1500 is affected by the heat, but maybe the 800 as well?
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Here is JRM weighing in on the previous thread
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Originally posted by tandfmanOriginally posted by SQUACKEEThe perfect weather for a track meet is 55 degrees, overcast and no wind. 8)
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Originally posted by ghOriginally posted by tafnutOriginally posted by abinfernoMy guess is any benefit is only measurable at velocities much higher than any sprinter can run.
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Originally posted by La_Spigola_LocaMy most simplified calculation for 10.00 at 0% humidity gives 9.95 at 100% hunidity.
Let's do this again. The average force of your "average elite" sprinter, say a 70 kg guy, is around 4000 N, applied about 25% of the time of the race. Let's simplify this and talk averages:
100m, 10.00 at 0% humidity.
4000 N *.25 = 1000 N
Let's assume 10 m/s is quick enough for a drag impact, where the force ius proportional to the square of the body's velocity, or F(drag) = qV^2, where V is the body's veocity, and q is the drag coefficient. q for your average guy (say 1.75 to 1.80, 70 to 75 kg) is about 0.45 kg/m. Now 0.45 kg/m * (10 m/s)^2 = F(drag) =~45 N, applicable throughout the race. So we can assume the guy applies on average 1045 N, out if which 45 are F(drag).
Now F(drag) is linearly dependent on air density. On going from 0% humidity to 100% we'd be changing air density by about 2% (at 20°C and atmospheric pressure, the difference is between 1.204 kg/m^3 and 1.176 kg/m^3), or decrease F(drag) by around 45 N *.02 =~0.9 N, which our sprinter can now put into his speed generating force, increasing it from 1000 N to 1000.9 N.
10.00/(1000.9/1000)^0.5 = 9.9955. So, not really a measurable difference there.137
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[quote=La_Spigola_Loca]Originally posted by "La_Spigola_Loca":14fsjl3lMy most simplified calculation for 10.00 at 0% humidity gives 9.95 at 100% hunidity.
Let's do this again. The average force of your "average elite" sprinter, say a 70 kg guy, is around 4000 N, applied about 25% of the time of the race. Let's simplify this and talk averages:
100m, 10.00 at 0% humidity.
4000 N *.25 = 1000 N
Let's assume 10 m/s is quick enough for a drag impact, where the force ius proportional to the square of the body's velocity, or F(drag) = qV^2, where V is the body's veocity, and q is the drag coefficient. q for your average guy (say 1.75 to 1.80, 70 to 75 kg) is about 0.45 kg/m. Now 0.45 kg/m * (10 m/s)^2 = F(drag) =~45 N, applicable throughout the race. So we can assume the guy applies on average 1045 N, out if which 45 are F(drag).
Now F(drag) is linearly dependent on air density. On going from 0% humidity to 100% we'd be changing air density by about 2% (at 20°C and atmospheric pressure, the difference is between 1.204 kg/m^3 and 1.176 kg/m^3), or decrease F(drag) by around 45 N *.02 =~0.9 N, which our sprinter can now put into his speed generating force, increasing it from 1000 N to 1000.9 N.
10.00/(1000.9/1000)^0.5 = 9.9955. So, not really a measurable difference there.[/quote:14fsjl3l]
Without going through the math in the limited time that I have it is my impression that at 100m speeds of 10m/sec, the wind resistence is greater than 4.5% of the effort. Now the figure that I remember from bicycling is that at 20mph most of the effort is overcoming wind resistence. At 10m/sec there is more running friction than other bicycle frictional losses. However, it would take a lot for the wind resistence to drop to 4.5%
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If you have any figures for me, that is, total force required to overcome air resistance, at a given speed and for a rider of a given weight, along with the ratio of the rider 's "surface area" (facing the wind) to the total surface area of the rider + bicycle, they're more than welcome. I had to use an "accepted" drag coefficient for "humans" of 0.45 kg/m (at a stretched position). Again, any value better than that is more than welcome.137
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Originally posted by La_Spigola_LocaIf you have any figures for me, that is, total force required to overcome air resistance, at a given speed and for a rider of a given weight, along with the ratio of the rider 's "surface area" (facing the wind) to the total surface area of the rider + bicycle, they're more than welcome. I had to use an "accepted" drag coefficient for "humans" of 0.45 kg/m (at a stretched position). Again, any value better than that is more than welcome.
I suppose that JMR knows more on this topic.
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Originally posted by 26mi235Another comment I remember that is running specific is that the reduction in wind resistence when drafting behind a runner at sub4 mile pace was 7%. The wind resistence should be just more than double at sprint speeds and I seem to remember that "drafting" reduces wind resistence by 30%, but certainly that depends on geometry and speed.
I suppose that JMR knows more on this topic.137
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