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Question

Two football players collide head on in midair, moving along the same horizontal direction, while trying to catch a thrown football. The first player is 94 kg and has an initial velocity of 5.95 m/s(in the positive direction), while the second player is 117 kg and has an initial velocity of -3.4 m/s

What is their velocity in the horizontal direction just after impact if they cling together, in meters per second?

? · Accepted Answer

initial positive momentum = 94(5.95) = 559.3 kgm/s
initial negative momentum = 117(-3.4) = -397.8 kgm/s
Σ initial momentum = 161.5 kgm/s
Σ final momentum = 161.5 kgm/s
horizontal final velocity* = 161.5/(94+117) ≈ 1.72 m/s 
*note:  + sign of 1.72 m/s indicates final direction of players is that of the 94 kg player's initial direction

Whome · Answer

conservation of momentum

mu₁ + Mu₂ = (m + M)v

v = (mu₁ + Mu₂) / (m + M)

v = (94(5.95) + 117(-3.4)) / (94 + 117)

v = 0.765 m/s

as the result is positive, it is in the direction of the smaller player's initial direction.

I hope this helped. 
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Please Help! 10 points best!?

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