Simple harmonic motion Need help Im studying

[NikkiNik]

Homework Statement

A spring, of negligible mass and which obeys Hooke's Law, supports a mass M on an incline which has negligible friction. The figure below shows the system with mass M in its equilibrium position. The spring is attached to a fixed support at P. The spring in its relaxed state is also illustrated.

Mass M has a value of 275 g. Calculate k, the spring constant.

The mass oscillates when given a small displacement from its equilibrium position along the incline. Calculate the oscillation frequency.

http://i32.photobucket.com/albums/d2/NikkiNik88/plot.png

Homework Equations

a=-k/m(x)
f= 1/2pi (sqrt(k/m))

The Attempt at a Solution

I used the mass given and .3m as x. I used the acceleration due to gravity for a.
I got -8.99 kg*m?? Is that correct

And for part b:
I used the equation above to solve for f
I got 0.9099 Hz

 

[rl.bhat]

Find the component of the acceleration due to gravity along the inclined plane. From the graph you can find the sinθ. Then find the force which pulls the spring down. Find the extension of the spring and then k.