physics emergency
posted by mary .
m1 = 2.7 kg block slides on a frictionless horizontal surface and is connected on one side to a spring (k = 40 N/m) as shown in the figure above. The other side is connected to the block m2 = 3.6 kg that hangs vertically. The system starts from rest with the spring unextended.
a) What is the maximum extension of the spring?

total mass = 6.3 kg
mass falls a distance x and nothing is moving when it reaches maximum spring extension x
potential energy lost by mass going down = m g x = 3.6 g x
that is potential energy gained by spring (1/2) k x^2
so
(1/2) k x^2 = 3.6 g x
x = 7.2 g/k 
how would you find the speed of the hanginf mass when the spring is extended 10cm?