
Simple Harmonic motion
I got this question in trig:
An object is attached to a spring. The object is pulled down 4 cm and released. It returns to its lowest point after 2 seconds. Write an equation modeling the position of the object as a function of time.
They don't say anything about a spring constant K, so I don't get it.

Since the object is undergoing simple harmonic motion we know the amplitude is 4cm and the period is 2 seconds. We also know that y(0)=4
Now just use this information to construct the appropriate Trig function.