Elastic Collision / Energy Preserved

Use energy conservation + conservation of momentum. You know that since the sliding block isn't losing energy to friction, that all it's energy must be in the form of kinetic and potential energy. At the point it's released, all of it's energy is in the form of gravitational potential energy. By the time it hits block 2, all of it's energy must be kinetic, so you'll be able to figure out the velocity of impact. Now, you combine what you know about energy-momentum conservation with the fact that block 1 is going to bounce a little back up the ramp, meaning you'll still have to look at gravitational potential energy and that should do it.