# Search results for query: *

1. ### Probability that A is smaller than B?

Yes, something to that effect. Is it possible to say "A is smaller than B X% of the time" ?
2. ### Probability that A is smaller than B?

Given two data sets A and B, we can, say, conduct ANOVA to see if the average is statistically different. Is there a way to determine what is the probabilty that A is smaller than B? Let's say that we can NOT assume anything about A and B e.g. if they follow a normal distribution.
3. ### Continuity and differentiability in two variables

Hi If the function ##f(x,y)## is independently continuous in ##x## and ##y##, i.e. f(x+d_x,y) = f(x,y) + \Delta_xd_x + O(d_x^2) and f(x,y+d_y) = f(x,y) + \Delta_yd_y + O(d_y^2) for some finite ##\Delta_x##, ##\Delta_y##, and small ##\delta_x##, ##\delta_x##, does it mean that it is continuous...
4. ### Analytical solution of Discrete-time Algebraic Riccati Equation

Homework Statement Solve for X in the DARE (Discrete-time Algebraic Riccati Equation) analytically. A is diagonal A = [-a\;0; 0 \;a], and B = [b; 0] (in MATLAB notation). Any help is very much appreciated! Homework Equations The DARE is given as A'XA - X - (A'PB+S)(B'XB+R)^{-1}(A'XB+S)' + Q =...
5. ### Linear Programming - satisfaction only at least one constraint

The LP I am concerned with has a number of inequalities. However, I need to only have at least one of them satisfied. This can be any combination of the inequalities, not a particular one. Say the LP has 5 inequalities to satisfy. I want to have that satisfying at least one of the 5 means...
6. ### Linear Programming - satisfaction only at least one constraint

Linear Programming - satisfaction of only at least one constraint Hi Is there a form of relaxation/modification of an LP of the form \text{min }\;\;f^\mathsf{T}x\\\mathbf{A}x\leq b such that if only anyone of the constraints is satisfied, then the solution ##x## is regarded as feasible...
7. ### Cross section - scattering of light by light

Homework Statement Red and green laser (wavelength of 650 nm and 532 nm respectively) are directed towards each other at 20 degrees. Each laser has 5 mW power, with diameter of 1mm. Assuming the intensity of the beams are decreased by 10% each after the 'collision', estimate the upper...
8. ### Thermodynamics - Simple mixing problem

Homework Statement Liquid ammonia at 1.5 MPa, 20oC is mixed with saturated vapor ammonia at 1.5 MPa at equal flow rate. At the outlet, 1.3 MPa and quality of 0.85. Calculate the heat transfer per kilogram of ammonia exiting the mixer. Homework Equations The Attempt at a Solution I tried...
9. ### Subsequent Measurements of two observables, compatible and incompatible pairs

Homework Statement On an arbitrary state, the observable \hat{A} is measured returning the result a. A compatible observable \hat{B} is then measured returning b. If \hat{A} is then measured again, is the same result a obtained? How about if \hat{A} and \hat{B} are not compatible...
10. ### What kind of food do astronauts eat?

I was wondering because they can't possibly bring 'normal' food for weeks/months of trip which need heaps of storage... or can they?
11. ### Gas expansion at constant pressure

specific heat, c would equal du/dT so I guess the heat supplied, q, would equal change in u = c dT but c is not given in the question.
12. ### Gas expansion at constant pressure

Hi ehild by applying heat and raising its temperature. However, I don't have/know an equation that equates total heating applied (Q) to the raise in temperature..
13. ### Gas expansion at constant pressure

Homework Statement 2 moles of gas at 300 K at 0.02 m3 is expanded to twice the original volume at constant pressure, and then adiabatically until T = 300 K again. assume monatomic gas. assume ideal. determine the final volume determine the heat supplied to the overall process determine...
14. ### Franck Hertz experiment - overheated tube

Homework Statement What happens when the tube is (a) overheated or (b) too cool. Homework Equations The Attempt at a Solution I searched on google and almost all said: " If the tube has been overheated, the emission current is small, and maxima and minima can hardly be recognized or...
15. ### Plotting on a number line

A little background: I am doing the Franck-Hertz experiment and was asked to plot the spacing of acceleration voltage between peaks of output (anode) voltage. Homework Statement Plot/sketch the resulting spacings with the uncertainties on a number line! Homework Equations The...
16. ### Hydrogen Wave Function

probability = \int\int \frac{1}{4}\frac{3}{2\pi}sin^{3}\theta e^{\phi} d\phi d\theta Should be probability = \int\int \frac{1}{4}\frac{3}{2\pi}sin^{3}\theta d\phi d\theta
17. ### Hydrogen Wave Function

...:smile: Nevermind. Found what's wrong...
18. ### Hydrogen Wave Function

Homework Statement Calculate the probability of finding the electron in a hydrogen within the angle \pm30\circ from the x-y plane.The hydrogen is in the (2,1,1) state. Homework Equations probability = \int\int\int\left|R_{2,1,1}\right|^{2} \left|Y^{1}_{1}\right|^{2} r^{2} sin(\theta) dr...
19. ### Input resistance (Input impedance)

Homework Statement A digital voltmeter is used to measure the resistance and voltage of a circuit. The resistance and voltage measured is used to calculate current flowing. What errors does the input resistance of the voltmeter introduce into the determination of current? Homework Equations...
20. ### V dot (dv/dt) = (0.5)*(d/dt)*(v^2) ?

Aha, I see. Or more elaborately: \frac{d}{dt}v^{2} = \frac{dv}{dt}\frac{d}{dv}v^{2} = \frac{dv}{dt}2v Thanks rock!
21. ### V dot (dv/dt) = (0.5)*(d/dt)*(v^2) ?

This is not a homework question, but a derivation in my class which I can't get around. Homework Statement Step1 F=ma Step2 \vec{F} = m\frac{d\vec{v}}{dt} Step3: Multiply both side by v \vec{F}.\vec{v} = m\vec{v}.\frac{d\vec{v}}{dt} Step4 Power = \frac{d}{dt}\frac{1}{2}m\vec{v}.\vec{v}...
22. ### Basic Quantum Physics - Particle(s) in a (3D) Box

It is a regular class. Yep, I'm fully aware of that. And I think n starts at 1 (111) since if one of them is 0, the wavefunction will also be equal to zero which is not true. Thanks for the help!:smile:
23. ### Basic Quantum Physics - Particle(s) in a (3D) Box

I do not know which permutations of n-values to choose though. My guess is that the question is asking for the sum of the lowest 10 energies, so choose 10 permutations of n-values giving the lowest energies and sum them up. Then times this sum by 2 since each energy is occupied by 2 neutrons...
24. ### Basic Quantum Physics - Particle(s) in a (3D) Box

I'm saying that only two neutrons can have the same permutation (combination) of n-values.
25. ### Basic Quantum Physics - Particle(s) in a (3D) Box

Hi bjnartowt, I honestly don't know about the principle. By the sound of it and after looking quickly at wikipedia, my understanding is that in this case, no three or more neutrons can have the same combination of ns (since each eigenstate can accept 2 neutrons). So I'm guessing that the...
26. ### Basic Quantum Physics - Particle(s) in a (3D) Box

Homework Statement A system of 20 neutrons are confined in the region 0<x<3L 0<y<L 0<z<2L With L=10^{-15}m If each eigenstate can accept 2 neutrons (corresponding to the 2 possible spin states) what is the total kinetic energy of the system? Homework Equations I found the...
27. ### Schrodinger's Equation in 1D

If I'm right this time, I was missing L2 And so I equate 0 = hbar2 - L2mE and also, after eliminating x2, I equate to the guess solution, and both of them give me a consistent answer: E = \frac{\overline{h}^{2}}{mL^{2}} Now, I think this is right! If it is, thanks very much :smile:
28. ### Schrodinger's Equation in 1D

Hi nickjer After putting it as a single fraction, I got: \frac{d^{2}\psi}{dx^{2}} = \left(\frac{-2}{\left(L^{2}-x^{2}\right)}\frac{x^{2}\left(\overline{h}^{2}-mE\right)+mL^{4}E}{L^{2}\overline{h}^{2}}\right)\psi I just cannot figure out how to remove the x dependencies in the numerator. If...
29. ### Schrodinger's Equation in 1D

Homework Statement An electron in a one dimensional crystal is bound by: U(x) = \frac{-\overline{h}^{2}x^{2}}{mL^{2}\left(L^{2}-x^{2}\right)} for \left|x\right| < L and x = infinity for \left|x\right| \geq L Show that a stationary state for the electron in the potential well \psi(x) =...
30. ### Zener Diode Regulator

Thanks very much for the clear explanation, K^2! I can see the where the formulas come from since you explanation fits my regulator well. However, there is one thing I need to clarify: is the threshold voltage 17V in the diagram? And you're saying that at low current e.g. 1mA in the diagram...
31. ### Zener Diode Regulator

My teacher was talking about power supply voltage regulators. I cannot get why does a zener diode regulator's output voltage drops after the load current through it exceeds some critical current? thanks in advance :smile:
32. ### De Broglie's Wavelength (matter wave)

Thanks vela.. the last part of the question says: If the neutron come originally from a U-235 nuclear fission reactor, in what sense are they now "cold"? I looked at wikipedia, and found "The neutron temperature, also called the neutron energy, indicates a free neutron's kinetic energy"...
33. ### De Broglie's Wavelength (matter wave)

:shy:...It does not do anything... I get it now that the 'slit system' is juts a diffraction grating and reading back my old notes about diffraction grating, the only difference is that now I cannot approximate sin(theta)=tan(theta)... sorry about my silliness..

35. ### De Broglie's Wavelength (matter wave)

I see :smile:. So now that I have lambda = 9.04e-11 m Can I use the equation (n-0.5)lambda = d sin(theta) with n = 1 and x = 20 tan(theta) so that x is the closest distance between the central maxima and the area of nearly zero flux? I am concerned since the problem states that...
36. ### De Broglie's Wavelength (matter wave)

Homework Statement Parallel beam of "cold" neutrons in the x-axis, with energy 0.1eV strikes a slit system in y-z plane. Slits are parallel to the y-axis 1 micron apart. What will be the distance between the detector at x=20m which records the highest flux of neutrons, and the closest one...
37. ### PARTIAL FRACTION Help

hi tiny-tim, you mean combine (add) them with (2s2-2)/(s2+1)2? so 1 = (2s3+s) + (2s2-2) then, where do I imply the A, B, C, and D? :confused: (thank you for your help so far) :smile:
38. ### PARTIAL FRACTION Help

oh, i mean: (As-Ai+Cs+Ci) + (B(s+i)2+D(s-i)2) = 1
39. ### PARTIAL FRACTION Help

They are 2s/(s2+1) or 0 and (2s2-2)/(s2+1)2 or 4si/(s2+1)2 so.. (As-Ai+Cs+Ci) / (s2+1) + (B(s+i)2+D(s-i)2) / ((s2+1)2) = 1 and As-Ai+Cs+Ci = 2s , B(s+i)2+D(s-i)2 = 2s2-2 is this right?
40. ### PARTIAL FRACTION Help

It is not good enough because I need to perform an inverse Laplace transform on the fraction. And at my level, I only use tables and some basic theorems (convolution, shift in s etc.) and 1/(s2 + 1)2) is not on the table :( I have attached my working using the first try..
41. ### PARTIAL FRACTION Help

Homework Statement How to break down: \frac{1}{(s^{2}+1)^{2}} into partial fractions? Homework Equations - The Attempt at a Solution I have tried: \frac{1}{(s^{2}+1)^{2}} = \frac{1}{(1+i)^{2}\times(1-i)^{2}} = \frac{A}{(s+i)} + \frac{B}{(s+i)^{2}} + \frac{C}{(s-i)}} +...
42. ### The Reverse Of 'char'

i know >>char(100) gives some kind of ascii letter as an answer my question is, is there a function to convert the ascii letter back to 100? Thank you! edit - The language is MATLAB
43. ### Can We Light a Match on the Moon?

Just watched the movie Avatar. Can we light up a match (or produce fire) where there's low/effectively no oxygen in the atmosphere e.g. moon? If not, can a spark still be produced? Thanks!
44. ### Microwave vs metallic objects

Does a microwave oven burns metallic objects? I never put spoons, forks, or aluminum foil inside a microwave because I'm afraid that the microwave oven will burn them. If I remember correctly, my brother put an aluminum foil inside and it burnt. Nonetheless, the interior of the microwave...
45. ### A Superball Colliding Inelastically with a Table

Use impulse (change in momentum) formula: Fave = I/\Deltat where I is the impulse i.e. final momentum minus initial momentum
46. ### Photoelectric effect

Hi When a photon of insufficient energy (lower that the metal's work function) arrive on the metal's surface, what will happen? One part of my notes says that it will be "reflected with no loss of energy", but my teacher has recently stated that it will be absorbed and emitted back as...
47. ### Cocktail Shaker: Ice Melting Explained

I used a cocktail shaker once in one of my friends' shop. It seems that ice blocks melt faster when shaken in a cocktail shaker (the shiny, metallic one) than in a regular plastic bottle. Why is this? is it just because the different material of the two bottles? Does a cocktail shaker has...
48. ### Static friction on inclined surface

well, i was just being a little bit fancy if you want, i think you can use Fd = \muN + Fs the previous equation: Fd \leq \muN + Fs just means that the force pulling the boy down must be less than or equal to the force holding the boy up (Fr and Fs) The only unknown variable is \mu...
49. ### Static friction on inclined surface

force down the slope: Fd = mg sin 560 normal force: N = mg cos 560 Friction holding the boy Fr = \muN maximum force provided by string Fs = 152 Equating forces: the string must not break so the boy doesn't fall, so Fd \leq \muN + Fs you can the solve for \mu, the coefficient...
50. ### Applying Newton's Laws Projected Up an Incline

You can solve the problem using the equations of motion vf2 = vi2 +2ad ---------(1) vf = vi + at --------(2) where vf and vi are the final and initial velocity respectively and a is the acceleration, t is the time Using equation (1), you can solve for d and using (2) you can solve for t...