<span>1.0 m/s
Momentum = mass x velocity
Total Momentum before any collision = total momentum afterwards
4.0 x 3.0= 12 :g x momentum before (x g because using weight)
Afterwards, if the velocity of the two joined is v then we get:
'momentum x g'=12v
so 12v=12
so v=1m/s</span>
