answer
1.1 m/s
explanation
momentum is conserved, so the total momentum of both cars is the same before and after the collision, where momentum is the product of mass and velocity
[tex]m_{1} v_{1} + m_2v_2=m_1v_3+m_2v_4[/tex]
m1 = 0.65 kg
m2 = 0.55 kg
v1 = 2.0 m/s
v2 = -3.0 m/s (negative because moving in opposite direction)
v3 = -1.3 m/s (since it bounces back, this is in the opposite/negative direction)
[tex]m_{1} v_{1} + m_2v_2=m_1v_3+m_2v_4[/tex]
[tex]0.65*2+0.55*-3=0.65*-1.5+0.55v_4\\1.3 + (-1.65) = -0.975+0.55v_4\\1.3 - 1.65 + 0.975 = 0.55v_4\\0.625 = 0.55v_4\\v_4 = 1.1[/tex]
