Momentum And Collisions 8

Question

Two football players collide head-on in midair while trying to catch a thrown football. The first player is 96.5 kg and has an initial velocity of 6.25 m/s, while the second player is 120 kg and has an initial velocity of −3.50 m/s. What is their velocity (in m/s) just after impact if they cling together? (Indicate the direction with the sign of your answer.)

m/s

Answer 1

This is an inelastic collision, but linear momentum is conserved.

 

M = 120 kg

v = velocity of M = -3.50 m/s

m = 96.5 kg

u = velocity of m = 6.25 m/s

w = speed of (M + m) after collision

 

Conservation of linear momentum:

 

Mv + mu = (M + m)w

 

w = (Mv + mu)/(M + m)

 

w = [120*(-3.50) + 96.5*6.25]/(120 + 96.5) m/s ≅ 0.846 m/s

 

The two stuck together move in the same direction as the first player, at a speed of 0.846 m/s