A steel marble is shot out of a launcher (straight) in a "catcher" on a ballistic pendulum. The pendulum then swings up into its max height ans stops. At that point...the height for the gPE is .163 m. The mass of the marble is .0558g. I need to find the inital velocity of the marble. I solve (.5)(m)(v^2)=mgh to find the starting velocity for that, which is the final velocity after the perfctly inelasic collusion. But what happens is that I use the perfctly inelasic collusion formula, m1v1 + m2v2 = (m1 +m2)v' , but I always end up with two variable because I don't know m2. This is where I get stuck. I know the velocity should be some where around 3.5, but I'm not getting close. Please help me..I attached a diagram, I hope it works.