Recent content by zachzach
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Graduate Comparing Best-fits of different data sets that have different noise levels
Suppose I have 2 sets of data: day1 and day2. I want to fit a model to both data sets and then compare them to each other to see which one fits the model the best (the fit is done with a computer using non-linear least squares method). The RMS of the fit would be fine except that day1 has much...- zachzach
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- Data Data sets Levels Noise Sets
- Replies: 1
- Forum: Set Theory, Logic, Probability, Statistics
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Graduate Does this differential equation have a nice solution?
\frac{dy}{dx} = \exp \left[ -x - e^{-x} \right] - y^2- zachzach
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- Differential Differential equation
- Replies: 1
- Forum: Differential Equations
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Projectile Motion: Comparison of Maximum Altitudes on Earth and Moon
That's what I got. Your tuition ended up being right.- zachzach
- Post #6
- Forum: Advanced Physics Homework Help
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Projectile Motion: Comparison of Maximum Altitudes on Earth and Moon
The initial velocity is zero? If that was true the projectile would not go anywhere. You wrote: 'A projectile is launched on the Earth with a certain initial velocity'. Also, think about what the velocity is at the maximum height.- zachzach
- Post #4
- Forum: Advanced Physics Homework Help
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Projectile Motion: Comparison of Maximum Altitudes on Earth and Moon
Yes, you are missing something. You are only using your intuition and not actual laws of physics. Try to prove your statement mathematically. Use equations of motion when the acceleration is constant (which is very close to being true when the projectile does not go too high).- zachzach
- Post #2
- Forum: Advanced Physics Homework Help
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Which Method Should Be Used to Calculate Energy in Standing Wave Formalism?
Your post is not written very well, but I think I may understand you. You can transform wavelength into frequency. My question is, how did you do this? Matter waves and light waves are different. They have different dispersion relations.- zachzach
- Post #2
- Forum: Advanced Physics Homework Help
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Pressure in Hydrostatic Equlibrium
Homework Statement Find the pressure as a function of r for the region r<< R where R is the radius of the object. The density goes as \rho = \rho_o {(\frac{r_o}{r})}^2. Homework Equations I know how to get to the answer my problem is dealing with the infinite density at r = 0.The Attempt at a...- zachzach
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- Equlibrium Hydrostatic Pressure
- Replies: 2
- Forum: Advanced Physics Homework Help
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Special Relativity Force and Linearization
Homework Statement Consider a particle moving at close to the speed of light with v \approx c \ \hat{z}. A small oscillatory force F(t) acts on the particle. Consider F(t) to be a first order (eg. linear) perturbation which will not effect v_o, only v_1, the first order component of v...- zachzach
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- Force Linearization Relativity Special relativity
- Replies: 1
- Forum: Advanced Physics Homework Help
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Graduate Nondegenerate Eignefunctions as Linear Combinations
Yes, I meant to write the equation that you did. So the answer is no then. You can never have a linear combination of non degenerate eigenfunctions that is itself an eigenfunction.- zachzach
- Post #3
- Forum: Quantum Physics
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Graduate Nondegenerate Eignefunctions as Linear Combinations
It is easily shown that two eigenfunctions with the same eigenvalues can be combined in a linear combination so that the linear combination is itself an eigenfunction. But what if the two eigenvalues are not the same? Can you still find a linear combination of the two functions that is an...- zachzach
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- Combinations Linear Linear combinations
- Replies: 3
- Forum: Quantum Physics
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Undergrad Dipole Moment of Two Electrons
Why is the dipole moment of two electrons equal to zero? \vec{d} = \sum{q_{i}\vec{r_{i}}} The distance between them is nonzero and they both have charges. It is not obvious to me why this sums to zero.- zachzach
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- Dipole Dipole moment Electrons Moment
- Replies: 1
- Forum: Electromagnetism
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Angular Momentum of Collapsing Cloud
That makes perfect sense. Thank you very much I have arrived at the correct answer.- zachzach
- Post #4
- Forum: Advanced Physics Homework Help
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Angular Momentum of Collapsing Cloud
Any help? PLEEEASE.- zachzach
- Post #2
- Forum: Advanced Physics Homework Help
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Angular Momentum of Collapsing Cloud
Homework Statement Beginning with \frac{d^2 r}{dt^2} = -G\frac{M_{r}}{r^2} , adding a centripetal acceleration term, and using conservation of angular momentum, show that the collapse of a cloud will stop in a plane perpendicular to its axis of rotation when the radius reaches r_{f} =...- zachzach
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- Angular Angular momentum Cloud Momentum
- Replies: 3
- Forum: Advanced Physics Homework Help
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Magnetism (determining the magnetic field)
Just draw the wire and set up a coordinate system. You know the wire goes N and S so you can label that. From those you can label E and W as well. Then "above the wire" is just above the plane of the wire or above sheet of paper.- zachzach
- Post #2
- Forum: Introductory Physics Homework Help