The damping ratio for a viscously damped spring-mass system, governed by the relationship $m \dfrac{d^{2}x}{dt^{2}}+c\dfrac{dx}{dt}+kx=F(t)$, is given by
- $\sqrt{\dfrac{c}{mk}} \\$
- $\dfrac{c}{2\sqrt{km}} \\$
- $\dfrac{c}{\sqrt{km}} \\$
- $\sqrt{\dfrac{c}{2mk}}$