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hjr
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Homework Statement
By substituting the proper equations I showed that the equation is right when time = phi/w.
Now when I make cos = o and sin = 1 and time = (pi/2 - phi)/w I can't solve the equation.
Homework Equations
If you need to see all the equations i can give it to you but I am pretty sure at this stage they are not needed. The original diff equation is:
m*dx^2 + b* dx + kx = F_nat*cos(wt)
with x equal to:
Asin(wt + phi)
A = F-nat/ mh where h = [tex]\sqrt{(\omega^{2}-\omega_{0}^{2})^{2} + b^{2}\omega^{2}/m^{2}}[/tex]
tan([tex]\phi[/tex]) = [tex]\frac{ (\omega^{2}-\omega_{0}^{2})}{\omega(b/m)}[/tex]
The Attempt at a Solution
when time = (pi/2 - phi)/w
i got:
F-nat/m * (k-mw^2) = f-nat * (w-nat^2 - w^2)
in my book in a different example you can solve for k and get mw^2 but then that side will be zero. But then the natural frequency has to equal the external forces frequency to make that side zero. I just need a hint. Sorry if this is all a mess. If you need anything clarify I will try my best to do it.
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