Two spheres in contact pushed at the left: what happens to each?

[alchemphy]

There are two spheres in contact in a row. The mass of the left one is m and the right is 2m. If there's a slight push of F to the right on the left ball. What would happen to the two balls?

Thanks!

 

[pixel01]

What would happen depends on the spheres, or whether it is a hard or soft impact

 

[alchemphy]

It's purely elastic.