A 4,600 kg open train car is rolling on frictionless rails at 21.1 m/s when it starts pouring rain. A while later the car's speed is 19.5 m/s. What mass of water has collected in the car? Provide your answer in appropriate units of meters (m), seconds (s), kilograms (kg), radians (rad) or combinations thereof, such as m/s or m/s^2. Use at least three significant figures in your answer, do not use scientific notation. Using more significant figures will not be considered incorrect; using fewer may lead to errors due to rounding.

A 4,600 kg open train car is rolling on frictionless rails at 21.1 m/s when it starts pouring rain. A while later the car's speed is 19.5 m/s. What mass of water has collected in the car? Provide your answer in appropriate units of meters (m), seconds (s), kilograms (kg), radians (rad) or combinations thereof, such as m/s or m/s^2. Use at least three significant figures in your answer, do not use scientific notation. Using more significant figures will not be considered incorrect; using fewer may lead to errors due to rounding.