Last night whilst watching the trampolining Liz Chetkovich noted that they now quote “time of flight” as one of the measurements that defines an athlete’s performance.
She then went on to say that this advantaged heavier athletes as they could depress the springs further when they landed, thus getting more push into the air.
Not quite right.
In layman’s terms, although the heavier athlete will indeed push the springs down further, the springs then have more weight to lift when they push him back into the air.
In fact, if you dropped two different weights onto a trampoline, and there were no energy losses in the system, and the springs obeyed Hooke’s Law perfectly, then both would bounce back into the air to exactly the same height from which they were dropped.
But of course there are energy losses in the system, and so they would not in reality rebound perfectly.
But the trampolinists of course continue to bounce high, and the reason simply is that they are putting energy into the system with their legs as they push off.
Thus the time of flight is determined not by the weight of the athletes, but by their power to weight ratio – their ability to generate the explosive power in their legs that will overcome gravity and push them higher into the air.