An open train car, with a mass of 2050 2050 kg, coasts along a horizontal track at the speed 2.17 2.17 m/s. The car passes under a loading chute and, as it does so, gravel falls vertically into it for 2.85 2.85 s at the rate of 453 453 kg/s. What is the car's speed v f vf after the loading is completed? Ignore rolling friction.