physics
posted by Nabil .
a 900 N running back moving at 2.0 m/s is stoppped in 0.70 seconds when hit by a lineback. What average foarce did the linebacker exert on the running back?
How much did the running back's momentum change?

F = m*a
900N = m*(9.8m/s^2)
m = 91.8367 kg
a = (change in velocity) / (change in time)
a = (Vf  Vi) / (change in time)
a = (2  0) / (.7) = 2.85714 m/s^2
F = 91.8367 kg * 2.8571 m/s^2 = 262.391 N 
change in momentum:
p = m*(change in velocity)
p = 91.8367 kg * (2 m/s) = 183.673 kg*m/s