Question

Please help

A 90 kg football player is running at 0.9 m/s. Assuming a head on collision, at what speed would a 110 kg football player have to run into the 90 kg
player in order to stop him

Answer 1

The two moments must be the same:

p1=p2

m1v1=m2v2

v2=(m1v1)/m2

v2=(90 kg x 0.9 m/s)/110kg=0.7 m/s