Simply Armonic Movement and k constant

  • Thread starter Thread starter Plat00n
  • Start date Start date
  • Tags Tags
    Constant Movement
Click For Summary
The discussion centers on the variable "k" in the context of harmonic simple movement and its relation to wave equations. The original poster questions whether "k" in the wave equation is the same as "k" in the Helmholtz equation. A correction is provided, indicating that the Helmholtz equation should include "k^2" rather than "k." After this adjustment, it is confirmed that both instances of "k" refer to the same value. The conversation clarifies the relationship between the equations and the correct formulation needed for consistency.
Plat00n
Messages
11
Reaction score
0
I have a question on "k" of an armonic simple movement.

If we take the equation of a wave, this is:

\frac {\partial \psi (x,t)}{\partial x^2} = \frac 1 v^2 \frac {\partial^2 \psi (x,t)}{\partial t^2}

And this, if I'm not wrong, must to satisfy the independent of time Helmholtz equation:

\frac {d^2 A(x)}{dt} + k A(x) = 0

I'm ok since here?

If it's ok, the solution of the first equation could be:

\psi (x,t) = A e^{kx-wt}

Is this "k" the same that the "k" in Helmholzt equation? Is there any mistake in this?

Plat00n.
 
Last edited by a moderator:
Physics news on Phys.org
Plat00n said:
I have a question on "k" of an armonic simple movement.
If we take the equation of a wave, this is:
\frac {\partial \psi (x,t)}{\partial x^2} = \frac 1 v^2 \frac {\partial^2 \psi (x,t)}{\partial t^2}
And this, if I'm not wrong, must to satisfy the independent of time Helmholtz equation:
\frac {d^2 A(x)}{dt} + k A(x) = 0
I'm ok since here?
If it's ok, the solution of the first equation could be:
\psi (x,t) = A e^{kx-wt}
Is this "k" the same that the "k" in Helmholzt equation? Is there any mistake in this?
Plat00n.


Nobody can help me a little?
 
Plat00n said:
I have a question on "k" of an armonic simple movement.
If we take the equation of a wave, this is:
\frac {\partial \psi (x,t)}{\partial x^2} = \frac 1 v^2 \frac {\partial^2 \psi (x,t)}{\partial t^2}
And this, if I'm not wrong, must to satisfy the independent of time Helmholtz equation:
\frac {d^2 A(x)}{dt} + k A(x) = 0
I'm ok since here?

Not quite. It should be:

\frac {d^2 A(x)}{dx^2} + k^2 A(x) = 0

If it's ok, the solution of the first equation could be:
\psi (x,t) = A e^{kx-wt}
Is this "k" the same that the "k" in Helmholzt equation? Is there any mistake in this?

If you use the corrected version of the equation that I posted, then yes the k's are the same.
 
The book claims the answer is that all the magnitudes are the same because "the gravitational force on the penguin is the same". I'm having trouble understanding this. I thought the buoyant force was equal to the weight of the fluid displaced. Weight depends on mass which depends on density. Therefore, due to the differing densities the buoyant force will be different in each case? Is this incorrect?

Similar threads

Replies
8
Views
1K
Replies
2
Views
1K
Replies
13
Views
1K
  • · Replies 1 ·
Replies
1
Views
1K
  • · Replies 3 ·
Replies
3
Views
1K
Replies
16
Views
2K
  • · Replies 11 ·
Replies
11
Views
3K
  • · Replies 4 ·
Replies
4
Views
1K
  • · Replies 11 ·
Replies
11
Views
858