question_answer

The car A of mass 1500 kg travelling at 25 m/s collides with another car B of mass 1000 kg travelling at 15 m/s in the same direction. After collision the velocity of car A becomes 20 m/s. Find the velocity of car B after the collision.

Answer:

car A	car B
\[{{m}_{A}}=1500kg\]	\[{{m}_{B}}=1000kg\]
\[{{u}_{A}}=25m/s\]	\[{{u}_{B}}=15m/s\]
\[{{v}_{A}}=20m/s\]	\[{{v}_{B}}=?\]

\[{{m}_{A}}{{u}_{A}}+{{m}_{B}}{{u}_{B}}={{m}_{A}}{{v}_{A}}+{{m}_{B}}{{v}_{B}}\] \[\Rightarrow 1500\times 25+1000\times 15\] \[\Rightarrow 1500\times 20+1000\times {{v}_{B}}\] \[\Rightarrow {{v}_{B}}=22.5\,\,m/s\]