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.

$kx=mg$

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