Damped harmonic oscillator physics

[brad sue]

Please I don't understand this problem at all:

Consider a driven damped harmonic oscillator.Calculate the power dissipated by the damping force?
calculate the average power loss, using the fact that the average of (sin(wt+phi) )^2 over a cycle is one half?

Please can I have some help for it?

B

 

[dicerandom]

Well, what's the differential equation which describes a damped harmonic oscillator? How does this differ from the normal harmonic oscillator equation? What, physically, causes this difference?

 

[brad sue]

Well, what's the differential equation which describes a damped harmonic oscillator? How does this differ from the normal harmonic oscillator equation? What, physically, causes this difference?

I know that x(t)= A*exp(alpha*t) *sin(wt+phi)
the diffierence come from the fact that the amplitude diminishes as t changes.