Law of Conservation of Energy on a pole vault?

Question

Assume that at the top of a pole vault, the athlete's speed is zero. The safety mat is 0.40m thick!

Apply the law of conservation of energy to determine the maximum speed with which the athlete lands after clearing the crossbar set at 4.6m

I realize that it might be a bit difficult because this will require both physics and sports knowledge, none of which I acquire

Answer 1

Let's start with what we know. The athlete is at rest at the top of the jump-- velocity zero, height 4.6m. He will accelerate at 9.8 m/s/s the whole way down.

However, the safety mat is 0.4m thick. He's actually going to free-fall (4.6- 0.4 = 4.2m) before starting to decelerate.

So, using:
V = Sqrt(2 * a * d)

V = Sqrt(2 * 9.8 * 4.2)

V = Sqrt(82.32)

V = 9.07 m/s

Answer 2

.5*m*v^2=m*g*h
h=4.6-0.4=4.2
v=sqrt(2*9.8*4.2)

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