Suppose two loaded train cars are moving toward one another, the first having a mass of 1.50 \times 10^5\, \mathrm{kg}1.50×10 5 kg and a velocity of (0.11 \, \mathrm{m/s})\, \hat{i}(0.11m/s) i ^ , and the second having a mass of 1.10 \times 10^5\, \mathrm{kg}1.10×10 5 kg and a velocity of (-0.21 \, \mathrm{m/s})\, \hat{i}(−0.21m/s) i ^ . what is their final velocity?