IThe pole vault landing pad at an Olympic competition contains what is essential

Question

IThe pole vault landing pad at an Olympic competition contains what is essentially a bag of air that compresses from its "resting" height of 1.1 m down to 0.3 m as the vaulter is slowed to a stop.

(a) What is the time interval during which a vaulter who has just cleared a height of 5.9 m slows to a stop?


(b) What is the time interval if instead the vaulter is brought to rest by a 21.4-cm layer of sawdust that compresses to 5.4 cm when he lands?

I got the Ans of (a)= 0.164 but what is the answer for (b) ?

Explanation / Answer

a) velocity = sqrt [2 a s] = sqrt [2 * 9.8 * (5.9 - 1.1) ] = 9.7 m/s

v2 - u2 = 2 a s

a = 9.72 / (2 * (1.1 - 0.3)) = 58.8 m/s2

t = v / a = 9.7 / 58.8

t = 0.164 s

b) velocity = sqrt [2 a s] = sqrt [2 * 9.8 * (5.9 - 0.214) ] = 10.56 m/s

v2 - u2 = 2 a s

a = 10.562 / (2 * (0.214 - 0.054)) = 348 m/s2

t = v / a = 10.56 / 348

t = 0.030 s

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