A linear elastic spring is 0.15m long. When the upper end is held in the hand and a 0.5kg mass is suspended from the lower end, its length becomes 0.220m. If the hand is now jerked quickly upward, the spring first extends to a length of 0.285m, then the mass starts to move up. The hand is then held still.

a)Calculate the acceleration with which the mass first begins to move.
b)Calculate the speeed of the mass when the length of the spring becomes 0.22m again.
c)Calculate the length of the spring when the mass comes to rest at its highest point

So Far.. a) Energy is conserved. Ee=Ek
Ee=Fx^2 /2
x= 0.285-0.15 (at maximum)
since the mass is not moving initially, there is neither work nor energy initially. Only enlastic energy is acting on it.
and then,,, i have no idea what to do