A runner runs 200m with +0.90m/s air at19.30 .can it be calculated how much time he would do without air?

Question

A runner runs 200m with +0.90m/s air at19.30 .can it be calculated how much time he would do without air?

Answer 1

If you're talking about the new World Record just set in Beijing by Usain Bolt, they were running into a head wind, therefore it should be -0.90 m/s

So, to correct Neo's calculation:

200 / 19.30 = 10.36 m/s

Without air = 10.36 + 0.90 = 11.26 m/s

200 / 11.26 = 17.76 s

However, as you can see, this is more than 1.5 seconds faster than the time achieved and this wind speed is less than half that allowed by the IOC rules.  So it's obviously far more complex than this, otherwise records would fluctuate wildly according to the prevailing conditions, which they don't.

Answer 2

no, you cannot calculate that, it depends on the human body, wind resistance, surface, other factors.

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Answer 3

a timely question...the time of Usain Bolt's world record performance in the 200 m race in the Beijing Olympics.

the first calculation is incorrect; the runner is NOT floating or flying in the air, so we cannot simply assume the velocities add as vectors.

we need a model for the force that is acting on the person as a result of the wind..we would likely start by using a simple model of air friction such as:

air friction = 1/2 d A C v^2

where d is the density of the air, A is the surface area of the runner exposed to the wind, and C is some coefficient of air drag (which is usually in the range of 0.2-0.5) and v^2 is the square of the runner's speed

clearly, to do a calculation accurately you would need to measure the surface area of the runner exposed to the wind, and would need to do some lab tests to find the value of C...but with all this, you could find the force acting on the runner due to the wind, and figure out how much the wind helps or hinders in a 200 m race

(please note...edited answer contains the important word NOT to describe the runner's motion)

Answer 4

Good isn't it corrects Neo's calculation but the both of them consider that only air resistance is limiting the runner's speed.  If you take away the headwind the runner will be able to go faster but he also has to do that. With a faster or longer stride the athlete's power output is dropping (even with no air resistance he cannot just keep going faster and faster over the ground) so how much of the theoretically possible time (based on air resistance alone) he can make up depends on his physiology.  It would need speed tests on the athlete's power output as well as on his wind resistance.

Answer 5

200/19.3 = 10.36 m/s

w/o air = 10.36 - .9 = 9.46m/s

200/9.46 = 21.13s