PHYSICS problem

Hello there, i need a specific answers to this problem, because i really don’t know how to solve it, these are the problems:

A cart A mass 2.0[kg] which is moving at a speed of 7.0[m/s] on a horizontal floor collides with the object B of mass 5.0[kg] which is standing still on the floor. After that, A and B are united and start sliding. There is no friction between cart and floor and the coefficient of sliding friction between B and floor is 0.20. Set the acceleration by gravity to 9.8[m/s2].

Find the speed of the object immediately after the collision.

A 2[kg] with 7[m/s] and B 5[kg] and the coefficient of sliding friction is u=0.2

i need the formula of these problems so that it can jive to my idea in programming…
these are going to use to my program…
help me please…