Step-by-step explanation:
It is given that,
Mass of the tackler, m₁ = 120 kg
Velocity of tackler, u₁ = 3 m/s
Mass, m₂ = 91 kg
Velocity, u₂ = -7.5 m/s
We need to find the mutual velocity immediately the collision. It is the case of inelastic collision such that,
![v=(m_1u_1+m_2u_2)/(m_1+m_2)](https://img.qammunity.org/2020/formulas/physics/college/nsz9d6lvmfvv8k6p86m7lwvwaqyfljw1qc.png)
![v=(120\ kg* 3\ m/s+91\ kg* (-7.5\ m/s))/(120\ kg+91\ kg)](https://img.qammunity.org/2020/formulas/physics/college/30fgvsfuy2kx4mybowve5ptsqhwqw19hto.png)
v = -1.5 m/s
Hence, their mutual velocity after the collision is 1.5 m/s and it is moving in the same direction as the halfback was moving initially. Hence, this is the required solution.