u(t) = displacement of the mass relative to its equilibrium position.
m = mass (m > 0)
γ = damping constant (γ ≥ 0)
k = spring (Hooke’s) constant (k > 0)
g = gravitational constant
L = elongation of the spring caused by the weight
F(t) = Externally applied forcing function, if any
u(t0) = initial displacement of the mass
u′(t0) = initial velocity of the mass