After successfully clearing the bar during the pole vault, CSLA’s star decathlet

Question

After successfully clearing the bar during the pole vault, CSLA’s star decathlete falls to the landing cushion which will break his fall. If his mass is 85 kg and he has a velocity of -11.5 m/s just prior to landing a). what is the linear momentum of the athlete just prior to impact ? b). how long does it take for his downward velocity to be reduced to zero by the landing cushion if the average net force on him once he hits the cushion is 2570 N? c.) 0.2 seconds after making contact with the mat, what was his velocity?

Explanation / Answer

a) momentum = mass x velocity

        = 85 x -11.5 = 977.5 kg m/s

b) a = F / m = 2570 / 85 = 30.24 m/s^2

using v = u + at

0 = -11.5 + 30.24t

t = 0.38 s

c) v = u + at

v = -11.5 + 30.24(0.2)

v = - 5.45 m/s

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