simple harmonic motion on a string

Hi

I need some clarification on this question

A light elastic string of natural length 50 cm and modulus 20 N has one end fastened to O on a smooth horizontal table. The other end has a particle of mass 0.4 kg attached to it and the particle is released from rest at a distance 60 cm from O. Find the time it takes to reach O.

While the string is stretched

T=kx/l

=20x/0.5

=40x

40x=-.4a

So,a = -100x

w=10

T=2pi/10 =pi/5

I get stuck from here. Can anyone help please? ThanksHi

I need some clarification on this question

A light elastic string of natural length 50 cm and modulus 20 N has one end fastened to O on a smooth horizontal table. The other end has a particle of mass 0.4 kg attached to it and the particle is released from rest at a distance 60 cm from O. Find the time it takes to reach O.

While the string is stretched

T=kx/l

=20x/0.5

=40x

40x=-.4a

So,a = -100x

w=10

T=2pi/10 =pi/5

I get stuck from here. Can anyone help please? Thanks