Consider a spring–mass–damper system with m = 100 kg, c = 20 kg/s, and k = 2000 N/m with an impulse force applied to it of 1000 N for 0.01 s. Compute the resulting response.
A 1000 N force acting over 0.01 s provides (area under the curve) a value of F^=FΔt=1000⋅0.01=10 N⋅s. Using the values given, the equation of motion is
100x¨(t)+20x˙(t)+2000x(t)=10δ(t)
Thus the natural frequency, damping ratio, and damped natural frequency are
ωn=1002000=4.427 rad/s,ζ=2100⋅200020=0.022,ωd=4.4721−0.0222=4.471 rad/s
Using equation (3.6), the response becomes
x(t)=mωdF^e−ζωntsinωdt (3.6)
x(t)=mωdF^e−ζωctsinωdt=0.022e−0.1tsin(4.471 t)