Question

What is their speed after the collision?

Answer 1

1st::: find the velocity of the mass which was released from A about to hit the other mass..using conservation of energy
2nd:::find their speed after collision...using conservation of linear momentum

Answer 2

What formulas I use?

Answer 3

for the 1st step...mgR=1/2mv^2
and mv=2mV
v=the velocity before the collision
and V= the velocity of the joined mass