physics problem?

Question

when a mass of 25 g is attached to a certain spring, it makes 20 complete vibrations in 4.0sec. what is the spring constant of the spring?

Answer 1

Freq = N/t = 20/4 = 5 Hz
Omega = 2*pi*Freq = 31.4159 rad/sec = sqrt(K/M)
K = Omega^2*M = 986.96*0.025 kg/sec^2 = 24.674 N/m
Note on units: kg/sec^2 = N/m because F (N) = MA (kg-m/sec^2).

Answer 2

m = 25 g
N = 20
t = 4 s
k = unknown spring constant

T = 2π/ω
T² = (2π)² / ω² = (2π)² m/k
T = t/N

Answer:
(2π)² m N² / t² = 6170 g/s² = 6170 dyn/cm