I am not sure how to do this, can someone explain to me how to solve this?

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

Question

I am not sure how to do this, can someone explain to me how to solve this?

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

vincent-lyon.fr · Answer

Use conservation of momentum just before and after the collision.

inexilewetrust · Answer

How exactly do i do that?

shamim · Answer

U hv to use the formula 
m1u1+m2u2=m1v1+m2v2

shamim · Answer

Response plz for better help

shamim · Answer

Given m1=1300kg
U1=2m/s

shamim · Answer

m2=1300+400=1700kg
u2=0
v1=v2=?

vincent-lyon.fr · Answer

You can also write :
m1u1+m2u2=(m1+m2)v

inexilewetrust · Answer

Thanks guys! I finished the test way before anybody responded. The formulas did help and I really appreciate it! I will write it down.