Four railroad cars, each of mass3.00 x 104 kg, are coupled together and coastingalong horizontal tracks at speed vi toward thesouth. A very strong but foolish movie actor riding on the secondcar uncouples the front car and gives it a big push, increasing itsspeed to 4.40 m/s south. The remainingthree cars continue moving south, now at 2.25 m/s.

(a) Find the initial speed of the cars.

m/s

(b) How much work did the actor do?

J