how to prove gravity=9.8 for a spring mass that obeys hookes law but mass +spring constant unknown ?

Question

thanks odu , but i am not quite thre yet ,

Answer 1

If you have the spring hanging vertically with no mass, and call the elongation 0, then hang the mass on the spring and let it come to equilibrium. The extension of the spring is
related as follows:
m*g=k*d
where d is the extension
so
g=k*d/m

Next, pull the mass down and release. The frequency of oscillation will be related as
f=w/(2*pi)
or
w=2*f*pi
we know that w=sqrt(k/m)
or
k/m=4*f^2*pi^2
plugging in above
g=4*f^2*pi^2*d

j