Three objects $A , B$ and $C$ are kept in a straight line on a frictionless horizontal surface. The masses of $A , B$ and $C$ are $m , 2 m$ and $2 m$ respectively. $A$ moves towards $B$ with a speed of $9 \mathrm {~m} \mathrm {~s} ^ { - 1 }$ and makes an elastic collision with it. Thereafter $B$ makes a completely inelastic collision with $C$. All motions occur along the same straight line. The final speed of $C$ is: (1) $6 \mathrm {~m} \mathrm {~s} ^ { - 1 }$ (2) $9 \mathrm {~m} \mathrm {~s} ^ { - 1 }$ (3) $4 \mathrm {~m} \mathrm {~s} ^ { - 1 }$ (4) $3 \mathrm {~m} \mathrm {~s} ^ { - 1 }$
Three objects $A , B$ and $C$ are kept in a straight line on a frictionless horizontal surface. The masses of $A , B$ and $C$ are $m , 2 m$ and $2 m$ respectively. $A$ moves towards $B$ with a speed of $9 \mathrm {~m} \mathrm {~s} ^ { - 1 }$ and makes an elastic collision with it. Thereafter $B$ makes a completely inelastic collision with $C$. All motions occur along the same straight line. The final speed of $C$ is:\\
(1) $6 \mathrm {~m} \mathrm {~s} ^ { - 1 }$\\
(2) $9 \mathrm {~m} \mathrm {~s} ^ { - 1 }$\\
(3) $4 \mathrm {~m} \mathrm {~s} ^ { - 1 }$\\
(4) $3 \mathrm {~m} \mathrm {~s} ^ { - 1 }$