Toy train P, with mass $0.50\,\text{kg}$, is moving on a straight track at a velocity of $3.0\,\text{m s}^{-1}$. It collides with toy train Q, which has mass $1.0\,\text{kg}$ and is at rest. The two trains then move together as one. What is the velocity of the combined trains?
- A$1.0\,\text{m s}^{-1}$ in the same direction as P was travelling originally
- B$1.0\,\text{m s}^{-1}$ in the reverse direction to that in which P was travelling originally
- C$1.5\,\text{m s}^{-1}$ in the same direction as P was travelling originally
- D$1.5\,\text{m s}^{-1}$ in the reverse direction to that in which P was travelling originally