A $2.0\,\text{kg}$ mass, moving at $3.0\,\text{m s}^{-1}$ across a frictionless surface, collides head-on with a $1.0\,\text{kg}$ mass that is initially at rest. The two masses join together after the impact. What kinetic energy is lost in the collision?
- Azero
- B$2.0\,\text{J}$
- C$2.4\,\text{J}$
- D$3.0\,\text{J}$