Speed machines
October 3rd 2008 01:24
Imagine the start line of a race. In Lane 1 we have a Ferrari, engine revving and hoping to show those fools who drool over McLaren F1s a thing or two. In Lane 2 we have a greyhound, standing calmly and hoping to earn a tummy rub. In Lane 3 we have a cheetah, hoping to have the greyhound for dinner.
The race distance is 30 metres - a pure test of acceleration. Who would win?
The Ferrari can accelerate from zero to 100 km/h in 3.2 seconds. So our Ferrari, the noisiest and least environmentally friendly of our race starters (but, admittedly, the only one with GPS and a sound system) is a worthy candidate in our race, right? Nah. The fact is, the other two have passed 30 metres before the Big Noisy Red machine has stopped spinning its tyres. Third place - every time.
The greyhound will cover the 30 metres in six strides and will have reached a speed of 70km an hour by the time it crosses the line. An elite human sprinter can reach 40km/h and a thoroughbred racehorse about 50 km/h. At full stretch, the greyhound is in contact with the track surface for only 25% of its stride distance - for the rest of the time it is, well, flying.
The cheetah can reach speeds of about 110 km/h over three to four strides from a standing start.
So, clearly, if you take the cheetah out, the greyhound wins our race and gets lots of tummy rubs and hugs. No, no, I'm not biased, I'm just saying ...
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