A model train engine of mass 0.60 kg travels along a straight, frictionless track and collides head-on with a stationary carriage of mass 1.50 kg. Following the collision, the carriage moves forward with a speed of 1.80 m s-1, while the engine recoils in the opposite direction with a speed of 0.70 m s-1. What was the initial speed of the engine?
1.52 m s−11.52\text{ m s}^{-1}1.52 m s−1
3.80 m s−13.80\text{ m s}^{-1}3.80 m s−1
4.50 m s−14.50\text{ m s}^{-1}4.50 m s−1
5.20 m s−15.20\text{ m s}^{-1}5.20 m s−1
