- #1
koab1mjr
- 107
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Hi all
I am struggling with going between various representations of vibrations in paticular the complex form.
I am using Rao as my text btw
so for a free vibration and making it simple no damping the euqation of motion is
[tex]mx^{..}[/tex] + kx = 0
with the general solution being
x = C1[tex]e^{iwnt}[/tex] + C2[tex]e^{-iwnt}[/tex]
Here is where the confusion starts, I am only suposed to consider the real portion of the solution above and disregard the imaginary. So using the euler identity becomes
x = (C1+ C2)cos(wnt) + (C1-C2)isin(wnt)
which is
Now based on the statement above i would disregard the second piece since its imaginary. but the problem is the book follws up with
x = C1'cos(wnt) + C2'sin(wnt) is including the second piece and now considering real. FRom here on I am fine but I am lost on this jump
Any help would be much apreciated.
Thanks
I am struggling with going between various representations of vibrations in paticular the complex form.
I am using Rao as my text btw
so for a free vibration and making it simple no damping the euqation of motion is
[tex]mx^{..}[/tex] + kx = 0
with the general solution being
x = C1[tex]e^{iwnt}[/tex] + C2[tex]e^{-iwnt}[/tex]
Here is where the confusion starts, I am only suposed to consider the real portion of the solution above and disregard the imaginary. So using the euler identity becomes
x = (C1+ C2)cos(wnt) + (C1-C2)isin(wnt)
which is
Now based on the statement above i would disregard the second piece since its imaginary. but the problem is the book follws up with
x = C1'cos(wnt) + C2'sin(wnt) is including the second piece and now considering real. FRom here on I am fine but I am lost on this jump
Any help would be much apreciated.
Thanks
Last edited: