Answer:
160 kg
12 m/s
Step-by-step explanation:
= Mass of first car = 120 kg
= Mass of second car
= Initial Velocity of first car = 14 m/s
= Initial Velocity of second car = 0 m/s
= Final Velocity of first car = -2 m/s
= Final Velocity of second car
For perfectly elastic collision
![m_(1)u_(1)+m_(2)u_(2)=m_(1)v_(1)+m_(2)v_(2)\\\Rightarrow m_2v_2=m_(1)u_(1)+m_(2)u_(2)-m_(1)v_(1)\\\Rightarrow m_2v_2=120* 14+m_2* 0-(120* -2)\\\Rightarrow m_2v_2=1920\\\Rightarrow m_2=(1920)/(v_2)](https://img.qammunity.org/2020/formulas/physics/college/hf0x62qrywkgl3arch6418m6fyep5pq02c.png)
Applying in the next equation
![v_2=(2m_1)/(m_1+m_2)u_(1)+(m_2-m_1)/(m_1+m_2)u_2\\\Rightarrow v_2=(2* 120)/(120+(1920)/(v_2))* 14+(m_2-m_1)/(m_1+m_2)* 0\\\Rightarrow \left(120+(1920)/(v_2)\right)v_2=3360\\\Rightarrow 120v_2+1920=3360\\\Rightarrow v_2=(3360-1920)/(120)\\\Rightarrow v_2=12\ m/s](https://img.qammunity.org/2020/formulas/physics/college/ocl7he0eheslf4bi9oc7m90cyqnk4gqqn4.png)
![m_2=(1920)/(v_2)\\\Rightarrow m_2=(1920)/(12)\\\Rightarrow m_2=160\ kg](https://img.qammunity.org/2020/formulas/physics/college/ytc96npomqamy1t5n1j9qw4folyavih99z.png)
Mass of second car = 160 kg
Velocity of second car = 12 m/s