Static and Dynamic Equilibrium EX 5

The forces acting on the block:

The acceleration of the block is zero and so, the sum of the forces exerted on the block is zero:

$F_S-F_G=0$

It follows from this equation that the magnitude of the force of the spring must be equal to the magnitude of the gravitational force.

$kx=mg$

$x=\frac{mg}{k}=\frac{(8)(10)}{5\times 10^3}=1.6\times 10^{-2}m=1.6cm$