\(20 \mathrm{~N}\)

a. Coulomb damping with a coefficient of friction of 0.3

b. Viscous damping with a damping coefficient \(1 \mathrm{~N}-\mathrm{s} / \mathrm{m}\)

c. Viscous damping with a damping coefficient \(2 \mathrm{~N}-\mathrm{s} / \mathrm{m}\)

d. Hysteretic damping with a hysteretic damping coefficient of \(12 \mathrm{~N} / \mathrm{m}\) at a frequency of \(4 \mathrm{rad} / \mathrm{s}\)

e. Quadratic damping \(\left(\right.\) force \(=a v^{2}\) ) with damping constant \(a=0.25 \mathrm{~N}-\mathrm{s}^{2} / \mathrm{m}^{2}\)