The initial momentum is p=m_{1}v_{1}+m_{2}v_{2}, where by boldfaced letters I denote vector quantities. Since the second blob is at rest, v_{2}=0. Then
p=m_{1}v_{1}; p=m_{1}v_{1}=2*3=6 kg*m/s;
In the closed system the total momentum is conserved. Therefore, the final momentum is also 6 kg*m/s, directed the same way as the initial momentum. However, since two blobs are now stuck together, the total mass is now M=m_{1}+m_{2}=2+2=4 kg. Therefore,
p=Mv=6=4v; From this v=6/4=1.5 m/s, directed the same way as the initial velocity of the first blob.
10/10/2013

Kirill Z.