Explanation:
We have,
Mass of the running back, m = 82 kg
Initial speed of the running back, u = +5.6 m/s
Final speed of the running back, v = -2.5 m/s
It is required to find the momentum change of the running back. For this we will subtract final momentum to the initial momentum. So,
[tex]\Delta p=m(v-u)\\\\\Delta p=82\times (-2.5-5.6)\\\\\Delta p=-664.2\ kg-m/s[/tex]
So, the magnitude of the change in momentum of the running back is 664.2 m/s in west direction.