Physics: Principles with Applications (7th Edition)

$3.2 \times 10^2 N/m$.
Use equation 11-6a to relate the period T=2.0s and the mass of m=32kg.. $$T=2 \pi \sqrt{\frac{m}{k}}$$ $$k=4 \pi^2\frac{m}{T^2}=4 \pi^2\frac{32kg}{(2.0s)^2} \approx 3.2 \times 10^2 N/m$$