Originally Posted by
Shidoshi
I've done some calculations and it's impossible for him to have reached even Mach 1.
Assuming constant gravitational acceleration (it varies from 9.81mē/s at sea level to 9.69mē/s at the start of his jump) and no friction.
He fell 119846ft (from 128000ft to 8154ft) in 4min19s = 259seconds.
So his average speed during the fall is Vavg = 36529m/259s = 141.04 m/s
His acceleration during fall is something of the form:
a = C - f(V), where f(V) is an always positive and monotonically increasing function of V that never exceeds C.
By that we can see that v(t) is a monotonically increasing, concave function (its first derivative is positive and its second derivative is negative).
Having that, the highest maximum velocity he could have had at the end of 259 seconds would be if his speed profile, v(t) was a straight line (no friction).
That velocity would be 2*Vavg = 242.08m/s or Mach 0.82
QED
Adding friction to the equation only lowers his maximum speed.
Disclaimer: This doesn't take away from the rest of the records he broke.
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