Given,
The mass of Johnny, m₁=73.0 kg
The mass of Francis, m₂=57.0 kg
The initial velocity of Johnny, u₁=3.0 m/s
The initial velocity of Francis, u₂=5.0 m/s
From the law of conservation of momentum, the total momentum of a system will always remain the same.
Therefore,
[tex]m_1u_1+m_2u_2=(m_1+m_2)v[/tex]Where v is the velocity with which they roll backward together.
On substituting the known values in the above equation,
[tex]\begin{gathered} 73.0\times3.0+57.0+5.0=(73.0+57.0)v \\ v=\frac{219+285}{130} \\ =3.88\text{ m/s} \end{gathered}[/tex]Thus the velocity with which they roll backward together is 3.88 m/s
