The scale of a spring balance reading from 0 to 250N has a length of 10.0 cm. A fish hanging from the bottom of the spring oscillates vertically at a frequency of 2.85 Hz.

Question

Ignoring the mass of the spring, what is the mass m of the fish?

(and why the heck do we have a fish on a spring?)

Answer 1

I am uncertain when is the length 10cm? When stretched with a 250N force?
if so, k=250/.1=2500N/m
If you are in a calculus based physics course, this is of some interest
http://www.kettering.edu/~drussell/Demos/SHO/mass.html
If you are in a plug and chug physics course, then

f=1/2PI *sqrt(k/m) and you solve for m.

Answer 2

thanks! i used the two equations for w0 and set them equal to each other and solved for m and it worked!

thanks!