posted by dan

The 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 0.1 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 6.9 m slows to a stop?

(b) What is the time interval if instead the vaulter is brought to rest by a 19.2-cm layer of sawdust that compresses to 4.6 cm when he lands?

(c) Qualitatively discuss the difference in average force the vaulter experiences from the two different landing pads. That is, which landing pad would exert the least force on the vaulter and why?

1. bobpursley

force*distance=1/2 mv^2=mgh

Olympics competition? Assume the vault was at 17 feet, or 5.2meters.

Energy to final stop: h=5.2m-.1m=5.1m
or GPE lost= mass*g*5.1m

Work done on the bag=GPE lost
Force*distance=mass*g*5.1
forceaverage= mass*g*5.1/1

now, consider momentum:
forceaverate*time= change in momentum
time= mass*vi/mass*g*5.1
= sqrt(2g*5.1)/g*5.1=sqrt (2/(g*5.1))
= .2seconds

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