Answer:
160 kg
12 m/s
Explanation:
[tex]m_1[/tex] = Mass of first car = 120 kg
[tex]m_2[/tex] = Mass of second car
[tex]u_1[/tex] = Initial Velocity of first car = 14 m/s
[tex]u_2[/tex] = Initial Velocity of second car = 0 m/s
[tex]v_1[/tex] = Final Velocity of first car = -2 m/s
[tex]v_2[/tex] = Final Velocity of second car
For perfectly elastic collision
[tex]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\times 14+m_2\times 0-(120\times -2)\\\Rightarrow m_2v_2=1920\\\Rightarrow m_2=\frac{1920}{v_2}[/tex]
Applying in the next equation
[tex]v_2=\frac{2m_1}{m_1+m_2}u_{1}+\frac{m_2-m_1}{m_1+m_2}u_2\\\Rightarrow v_2=\frac{2\times 120}{120+\frac{1920}{v_2}}\times 14+\frac{m_2-m_1}{m_1+m_2}\times 0\\\Rightarrow \left(120+\frac{1920}{v_2}\right)v_2=3360\\\Rightarrow 120v_2+1920=3360\\\Rightarrow v_2=\frac{3360-1920}{120}\\\Rightarrow v_2=12\ m/s[/tex]
[tex]m_2=\frac{1920}{v_2}\\\Rightarrow m_2=\frac{1920}{12}\\\Rightarrow m_2=160\ kg[/tex]
Mass of second car = 160 kg
Velocity of second car = 12 m/s
