Step-by-step 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,
![\Delta p=m(v-u)\\\\\Delta p=82* (-2.5-5.6)\\\\\Delta p=-664.2\ kg-m/s](https://img.qammunity.org/2021/formulas/physics/high-school/vhzvp4eo4ceqbp7ltbc1oes3cvz9eykc6o.png)
So, the magnitude of the change in momentum of the running back is 664.2 m/s in west direction.