Harmonic oscillator - The spring

This applet simulates the motion of a spring having mass , elastic constant , and resting length equal to 4 units. The motion is approximated by a uniformly accelerated one during a time interval .
Set the initial elongation of the spring by positioning the point and its initial velocity , then click on Initialise and subsequently on Start. Find a suitable time interval where the approximation is good according to expectations (the simulated motion is not damped by any frictional force): you should get a periodic motion. Experimenting with various values of and can you find a relation among the period and the spring parameters? [Hint: to obtain a sutable measure of the period you can look at points where the graph meets the abscissa axis] Set the initial velocity to and check your findings by means of the cosine function.