Answer:
f= 1/2pi*sqrt(g/static elongation)= 1.08 Hz
Explanation:
explanation at equilibrium mg= k*static elongation k= mg/static elongation frequency= sqrt(k/m)/2pi= sqrt(g/static elongation)/2pi
OR
k = w / 0.21N/m
= mg / 0.21
where m = mass
m/k = 0.21 / 9.8 = 0.0214
period of SHM
= 2 pi sq root [ m/k]
= 2 * pi * sq rt 0.0214
= 0.919 s
Frequency = 1/ 0.919 = 1.08 Hz