Calculate the final velocity right after a 114 kg rugby player who is initially running at 7.95 m/s collides head‑on with a padded goalpost and experiences a backward force of 17900 N for 5.50×10−2 s. final velocity:/? m/s
Let us consider the direction of the initial velocity of the rugby player as positive.
Mass of the rugby player = m = 114 kg
Initial velocity of the rugby player = V1 = 7.95 m/s
Final velocity of the rugby player = V2
Force exerted by the goalpost on the player = F = -17900 N (Negative as it is in the backward direction)
Time period the player experiences this force = T = 5.5 x 10-2 sec
Impulse of the goalpost on the player = I
I = FT
Impulse is equal to the change in momentum,
I = mV2 - mV1
FT = m(V2 - V1)
(-17900)(5.5x10-2) = (114)(V2 - 7.95)
V2 - 7.95 = -8.636
V2 = -0.686 m/s
The negative sign indicates the player is moving in the opposite direction of his initial motion.
Final velocity of the rugby player = -0.686 m/s
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