A rectangular block of mass $5 \mathrm{kg}$ attached to a horizontal spiral spring executes simple harmonic motion of amplitude $1 \mathrm{m}$ and time period $3.14 \mathrm{s}$. The maximum force exerted by spring on block is ___ $\mathrm{N}$.

By Newton's second law,

$F=m{a}_{max}$.

The maximum acceleration for a SHM is given by 

$a_{max}={\omega }^{2}A ...\left(i\right)$

The time period is given by 

$T=\frac{2\pi }{\omega }=3.14 \mathrm{s}$

$\Rightarrow \omega =\frac{2\pi }{T}=\frac{2\pi }{3.14}=2 \mathrm{rad} {\mathrm{s}}^{-1}$

Thus, the maximum acceleration from equation (i)

$a_{\mathit{m}\mathit{a}\mathit{x}}=4\times 1=4 \mathrm{m} {\mathrm{s}}^{-2}$

The maximum force is 

$F=5 \mathrm{kg}\times 4 \mathrm{m} {\mathrm{s}}^{-2}=20 \mathrm{N}$