But wait. Lyles is wearing a hefty chain, and the watch itself probably weighs about 150 grams. So let’s say the mass of the jewelry is 250 grams instead of 10. In that case, we would get 99.61 percent of the acceleration of our base model. Still a compact difference. If I were a running coach, I’d say if the chain makes you feel good, then go for it!
Running with hair
What about hair? Does it matter whether you pull your hair back or let it flow behind you? In this case, it’s not about the extra mass, but about air resistance. This is more complicated, but again we can get a abrasive estimate. One model of drag looks like this.
BY AUTHORIZATION OF RHETTA ALLAIN
The drag force increases with speed (In), air density (R), cross-sectional area of the channel (AND) and their shape (represented by the drag coefficient C). So as the runner increases speed, the drag force also increases. Some say that this causes the runner to achieve a constant speed. But that can’t be true – otherwise you could run infinitely brisk on a treadmill, where there is no air resistance.
Now let’s add that force to a runner in the acceleration phase of a 100-meter sprint. Although humans are very complicated, we can get an estimate of drag by looking at a skydiver. When a person jumps out of an airplane, they raise their speed until the downward pull of gravity (mass times gravitational field) equals the upward push of air resistance. This is called terminal velocity, and for a normal person it is about 120 miles per hour (54 meters per second).
If we consider a 65 kg person, the value of all the things that are before the velocity in the equation will be 0.218 Ns2/M2. (Just trust me and don’t worry about these complicated units.)
When I add this drag force to the model, I get a 100-meter time of 11.9884 seconds and a maximum speed of 10.6822 meters per second.
Now let’s say you have really hefty hair. In the extreme, that could raise the cross-sectional area of the runner by 1 percent. That means the constant before the velocity would also raise by 1 percent. Great. That’s a run time of 11.9925 seconds. Oh boy. You just shaved 0.0041 seconds off your time. Speaking as a guy who has almost no hair, I’d say it’s totally worth it.