Simple Harmonic Motion oscillations

[kingyof2thejring]

A 0.49 kg mass attached to a spring (k = 19.8 N m-1) is performing SHM on a smooth horizontal surface. Calculate the periodic time of these oscillations, in s.

what equation links with T=2pi/w to give T or how do i use a=-ky/m.
thanks in advance

 

[kingyof2thejring]

if
F=ma= m*d^2y/dx^2 = -m*w^2*y = -ky
i get T=0.988

 

[El Hombre Invisible]

The linking equation you're looking for is:

$$k = m\omega^2$$