In a deep-space docking maneuver, a robotic spacecraft A A\,A of mass 120 kg is traveling at 6.0 m s-1 along a straight line. It collides with spacecraft B B\,B of mass 180 kg traveling at 4.0 m s-1 along a straight line perpendicular to the path of AAA. Upon impact, the two spacecraft latch together to form a single combined unit.
What is the magnitude of the velocity of the combined unit immediately after the collision?
2.4 m s−12.4\text{ m s}^{-1}2.4 m s−1
4.8 m s−14.8\text{ m s}^{-1}4.8 m s−1
3.4 m s−13.4\text{ m s}^{-1}3.4 m s−1
5.0 m s−15.0\text{ m s}^{-1}5.0 m s−1