Answer:
y = 16sin(2Ï€/ 3)t.
Step-by-step explanation:
When displacement = 0 at time = 0 we use the sine function.
The formula is y = A sin(2πft)  where A = the amplitude, f = frequency which  is 1/period and t = the time.
So for this SHM the function is
y = 16sin(2Ï€/ 3) t.
You are correct.