Elastic collision on air track, finding center of mass speed

[sstangle73]

A cart with mass 370 g moving on a frictionless linear air track at an initial speed of 1.7 m/s undergoes an elastic collision with an initially stationary cart of unknown mass. After the collision, the first cart continues in its original direction at 0.42 m/s.
(a) What is the mass of the second cart?
223.3 g
(b) What is its speed after impact?
2.12 m/s
(c) What is the speed of the two-cart center of mass?
?? m/s

Cant get part c?
Any help is appreciated

 

[ehild]

How is the center of mass defined?

ehild

 

[sstangle73]

That is all the information given

 

[ehild]

You have to know the definitions of terms in a problem. What have you learned about center of mass?

Read this: http://online.physics.uiuc.edu/courses/phys211/spring10/Text/ch10.pdf

ehild