In: Physics
The motion of a forced damped spring system is:
?(?) = 2 sin 4? + ? ^-? cos 6?.
A) What is the driving frequency?
B) What is the transient part?
C) What is the steady-periodic part?
Could someone provide explanations as to how to obtain these solutions as I am lost?
The solution to the differential equation of a forced damped spring system driven by an external force has two parts, a transient part and a steady-state part, which must be used together to fit the physical boundary conditions of the problem.
The general solution is a sum of a transient solution that depends on initial conditions, and a steady state that is independent of initial conditions and depends only on the driving amplitude F0, driving frequency ω.
The transient part must contain a damping part in terms of a negative exponential.
The solution given to us is
?(?) = 2 sin 4? + ? ^-? cos 6?.
Clearly , the second part on the RHS contains the damping part ( e^-t) and hence , it is the transient part. (PART B)
The first part on the RHS is independent of the initial conditions and does not contain any damping part, and hence, it is the steady-periodic part. ( 2 sin 4?) (PART C)
The steady periodic part is due to the driving force. Thus, comparing 2 sin 4? with A sin (wt) gives the angular driving frequency w=4.
Hence, Driving frequency = w/(2*) = 4/(2*) = 2/ (PART A)