I am still unsure about how you end up with 2x though. Could you explain?
Sure, but people have been known to get upset, create fake accounts, and start fights about definitions, etc when I start using math, so I try to avoid it now.
Physics simplifies things to begin with, and I am going to have to simplify things even more.
Drag force = 1/2 "fluid density" * area * "drag coefficient" * velocity^2
We are comparing swimming to cycling, so we don't care about actual numbers, just the ratios between the two, except velocity. Luckily, we have real velocity numbers.
The drag coefficient difference between a streamlined body and a sphere is 10x. When compared to a swimmer, a cyclist isn't very streamlined, so lets assume 10x difference between the two. Now the area facing the resistance is also quite different between a swimmer and a cyclist, so lets also assume a 2x difference. We don't care about the 1/2, since it is canceled out. To keep things simple, water density is 1000 and air density is 1.
Now we have
"Drag force of swimming"/"Drag force of cycling = (1000*1*1*"swimming velocity"^2)/(1*10*2*"cycling velocity"^2)
This is where I make a mistake. I don't know anything about cycling, so I assumed 25mph for the cyclist and 5mph for a swimmer, but I forgot to convert to m/s.
(1000*1*1*5^2)/(1*10*2*25^2) = 2
That is where I got my 2x. Using 2 m/s for the swimmer and 11m/s for the cyclist we get:
(1000*1*1*2^2)/(1*10*2*11^2) = 1.7
Considering power and especially energy, cyclist really do care, or should care, a lot about air resistance.
And my point wasn't that 2x is correct, but point was that people neglect air, but at racing speed for a cyclist, it is a significant factor.
I don't know ANYTHING about cycling but I know over a 90 hour race, a huge amount of calories will be spent just cutting through the air. I have to think that more calories are spent on air resistance by cyclists than swimmers spend on water resistance even if I am hugely wrong with my coefficient of drag and area ratios.
What do cyclists think they spend all their energy on?
So you would think it's a technique, that most should learn?
Cycling is a dangerous sport to begin with. I am not qualified to give advice on cycling, but it does seem like the sport is being trivialized in the thread.
I am still unsure about how you end up with 2x though. Could you explain?
Sure, but people have been known to get upset, create fake accounts, and start fights about definitions, etc when I start using math, so I try to avoid it now.
Physics simplifies things to begin with, and I am going to have to simplify things even more.
Drag force = 1/2 "fluid density" * area * "drag coefficient" * velocity^2
We are comparing swimming to cycling, so we don't care about actual numbers, just the ratios between the two, except velocity. Luckily, we have real velocity numbers.
The drag coefficient difference between a streamlined body and a sphere is 10x. When compared to a swimmer, a cyclist isn't very streamlined, so lets assume 10x difference between the two. Now the area facing the resistance is also quite different between a swimmer and a cyclist, so lets also assume a 2x difference. We don't care about the 1/2, since it is canceled out. To keep things simple, water density is 1000 and air density is 1.
Now we have
"Drag force of swimming"/"Drag force of cycling = (1000*1*1*"swimming velocity"^2)/(1*10*2*"cycling velocity"^2)
This is where I make a mistake. I don't know anything about cycling, so I assumed 25mph for the cyclist and 5mph for a swimmer, but I forgot to convert to m/s.
(1000*1*1*5^2)/(1*10*2*25^2) = 2
That is where I got my 2x. Using 2 m/s for the swimmer and 11m/s for the cyclist we get:
(1000*1*1*2^2)/(1*10*2*11^2) = 1.7
Considering power and especially energy, cyclist really do care, or should care, a lot about air resistance.
And my point wasn't that 2x is correct, but point was that people neglect air, but at racing speed for a cyclist, it is a significant factor.
I don't know ANYTHING about cycling but I know over a 90 hour race, a huge amount of calories will be spent just cutting through the air. I have to think that more calories are spent on air resistance by cyclists than swimmers spend on water resistance even if I am hugely wrong with my coefficient of drag and area ratios.
What do cyclists think they spend all their energy on?
So you would think it's a technique, that most should learn?
Cycling is a dangerous sport to begin with. I am not qualified to give advice on cycling, but it does seem like the sport is being trivialized in the thread.
