## anonymous 4 years ago A single 1,300 kg cargo train car is rolling along a train track at 2.0 m/s when 400 kg of coal is dropped vertically into it. What is its velocity right afterward? Assume a closed system. 1.5 m/s 2.0 m/s 6.5 m/s 0.0011 m/s

1. JamesJ

Use Conservation of Momentum. The momentum of the train before the coal added is equal to the momentum after the coal is added. See what to do now?

2. anonymous

not really :(

3. anonymous

The definition of momentum is$\vec p = m \vec v$So if momentum before the coal is dropped must equal the momentum before this event occurs. $\vec p_i = \vec p_f$Hopefully you can see what to do now!