How are the direction of an oscillator's displacement and the direction of the oscillator's acceleration related?

What is hidden during a lunar eclipse? isn't the moon hidden?

The 10-kg double wheel with radius of gyration of 125mm about o is connected to the spring of stiffness k = 600 n/m by a cord which is wrapped securely around the inner hub. if the wheel is released from rest on the incline with the spring stretched 225 mm, calculate the maximum velocity v of its center o during the ensuing motion. the wheel rolls without slipping

What are two different ways you could find the value of a? explain these methods.