A 10,500kg railroad car travels alone on a level, frictionless track with a constant speed of 15.0 m/s. An additional 5,000kg load is dropped from a tower onto the car. What will then be its new speed? 2. Relevant equations Momentum of conservation: m1i+m2i=(m1+m2)vf 3. The attempt at a solution Plugging in the numbers i get: 10,500kg(15m/s) + 0 = (10,500 kg+5000 kg)vf 157500kgm/s+0=(15,500kg)vf 10.16 m/s=vf vf=10.2m/s is this correct?