In order to determine the acceleration of the block, use the following formula:
Moreover, remind that for an object attached to a spring the magnitude of the force acting over a mass is given by:
Then, you have:
by solving for a, you obtain:
In this case, you have:
k: spring constant = 100N/m
m: mass of the block = 200g = 0.2kg
x: distance related to the equilibrium position = 14cm - 12cm = 2cm = 0.02m
Replace the previous values of the parameters into the expression for a:
Hence, the acceleration of the block is 10 m/s^2