Bubka makes things look too easy. Running while carrying a pole (over two times one's height) presents some elemental difficulties. Yet, Bubka manages to do it for a total of twenty steps, as evidenced in the video in the previous post.
In pole vaulter world, this epic run is not spoken of in terms of total steps. We count the number of times the left foot takes a stride. Bubka took twenty steps, but a pole vaulter would say that he vaulted from a ten-stride.
At the high school level, girls at the competitive state level usually run from around a seven-stride. This may not sound like such a big difference to the layman ("Seven is almost ten, right?"), but a coach once told me that every one increase in stride means vaulting a foot higher. And that's a gargantuan difference in a sport like track and field, where records are beaten by milliseconds or half inches.
It still seems a bit unbelievable, however, that a mere two steps would catapult the vaulter an entire foot higher. But we've already found how a vaulter's velocity relates to the height he can vault. So let's calculate if this really is true.
Two running steps is about 11 feet for the high school female, believe it or not (when my coach tells me to go from a six-stride to a seven-stride, he tells me to go back 11 feet). I would estimate two of Bubka's steps to be about 15 feet, or 4.572 meters.
We calculated in a previous post that Bubka's final velocity is 11.0 m/s. Based on the video of his record jump, his total run is timed to be about 6 seconds. This gives us enough to calculate his average acceleration.
a = (v1 - v0) / t
a = (11.0 m/s - 0 m/s) / 6
a = 1.83 m/s2
Of course, in real life, Bubka's acceleration wouldn't remain constant throughout his run. His acceleration would be very high in the beginning of his run, and as he approached his maximum speed, his acceleration would decrease. However, for the purpose of estimation, let's assume that Bubka's acceleration does remain constant.
v12 = v02 + 2ad
v12 = (11.0 m/s)2 + 2 (1.83 m/s2) (4.572 m)
v12 = 137.733
v1 = 11.736 m/s
Bubka's final velocity if he had run one stride more would be 11.736 m/s. How high would he jump?
v = √19.62h
11.736 = √19.62h
137.733 = 19.62h
h = 7.02 m = 23.03 ft
So is it possible to increase vaulting height by one whole foot by adding a stride? Yes, yes it is. By adding a stride to Bubka's world record vault, we calculated that he could vault almost three feet higher. Remember, however, that we estimated Bubka's acceleration to be higher than it really is, for ease of calculation, so in reality, a one-stride increase would probably bring the vaulter about one foot higher.
And now you should have mad respect for pole vault coach wisdom. But you may be asking yourself, why didn't Bubka just run from two steps back? To quote one of the best coaches of all time-- "If pole vaulting were that easy, everyone'd be good at it."
