I am struggling with the second part of this problem. It reads this way:
A particle P of mass 0.8kg is attached to one end of a light elastic string of natural length 1.6m and modulus of elasticity 20N. The other end of the string is fixed to a point O on the smooth horizontal surface on which P rests. The particle is held at rest with OP = 2.6m and then released.
a)Show that the, while the string is taut, P moves with simple harmonic motion.
b)Calculate the time from the instant of release until P returns to its starting point for the first time?
How do I start the b part? Please help!!!