# Search results

1. ### Stupid question - is it possible to use up all the oxygen in your room?

And how long would it take to run out of oxygen? I often wonder if there's a tiny little gap of say, 1 square cm to the outside world, would you rate of oxygen consumption beat the inflow of oxygen?
2. ### Stupid question - is it possible to use up all the oxygen in your room?

I have a stupid question to ask you all. Let's just say that you shut your door, and then shut all your windows so there isn't any ventilation and stayed in your room for several days. Could you end up breathing until you've reduced the oxygen to dangerous levels?
3. ### Matlab matched filter question

Homework Statement Our job is to recreate the system in the above diagram in Matlab. I've been able to do all the stages effectively except the "matched filtering" part. Homework Equations The Attempt at a Solution I don't really understand matched filtering very well. I...
4. ### Nabla Operator Question

=\frac{-r\hat{r}}{r^{3}} ?? so it's the negative r unit vector pointing in the r direction.. over r cubed.. right? =( I seem to have a huge knowledge hole about vectors
5. ### Nabla Operator Question

I don't understand the differences between: \vec{r},\hat{r} and r! =(
6. ### Nabla Operator Question

I'm thinking hard but I'm not sure.. I'm thinking something along the lines of.. the x-component of \hat{r}.. the y-component. or something? >_<
7. ### Nabla Operator Question

r^{2} = x^{2}+y^{2}+z^{2}? - \hat{r} = -x \hat{e_1}-y\hat{e_2}-z \hat{e_3}? So final answer: \frac{-\hat{r}}{r^{5/2}} ?
8. ### Nabla Operator Question

Is this better? I can't figure out how to simplify it further.
9. ### Nabla Operator Question

Does my solution look correct to you guys? Homework Statement Calculate: \nabla \varphi (r) If: \varphi (r) = \frac{1}{4\pi\epsilon_{0}}\frac{1}{r} with: r = \sqrt{x^{2}+y^{2}+z^{2}} Homework Equations n/a The Attempt at a Solution
10. ### Do these solutions look vaguely correct?

Quantum mechanics without really knowing what is going on - that is an accurate description. I'm studying electronic engineering - but we're all forced to take on this subject which is called Electronc Materials. I'm finding it tough with little to no background in Physics. Anyway, I've...
11. ### Do these solutions look vaguely correct?

What do you mean by bound states? I'm really sorry to be such a newbie.!
12. ### Do these solutions look vaguely correct?

Must I have a value for Vo to find the eigenenergy values? In all the examples my teacher has ever given, he always seems to write Vo, but not actually specify what it is.
13. ### Do these solutions look vaguely correct?

yep. S = e^{-a} \ \ \ \ \ -e^{-jk} \ \ \ \ \ -e^{jk} \ \ \ \ \ 0 ae^{-a} \ \ \ \ \ -jke^{-jk} \ \ \ \ \ jke^{jk} \ \ \ \ \ 0 0 \ \ \ \ \ e^{jk} \ \ \ \ \ e^{-jk} \ \ \ \ \ -e^{-a} 0 \ \ \ \ \ jke^{jk} \ \ \ \ \ -jke^{-jk} \ \ \...
14. ### Do these solutions look vaguely correct?

the x-axis is Ehat - the energy, normalised. So: Ehat = E \frac{L}{2}, where L is the length of gap in my "well" and the y-axis is detS - the determinant of the matrix I created from the boundary and interface conditions. So each x-axis crossing should give me an energy eigenvalue shouldn't...
15. ### Do these solutions look vaguely correct?

Homework Statement I wrote a whole heap of MATLAB code, and I have no idea whether my answers, or the plots of my answers are anywhere in the vicinity of looking right. I was hoping someone with a lil bit of experience in this type of physics would be able to tell me if I'm on the right...
16. ### Stuck on a 'normalisation' step

Sorry! I've edited my above post.. Now it makes more sense :) What I'm really after is how did they (my teacher) come up with [E] and what is it? k_hat is apparently a normalised k
17. ### Stuck on a 'normalisation' step

Hey guys, Homework Statement I have an assignment, which is to Solve Schrodinger's equations, for a certain potential distribution, which can be divided up into three regions. A solution for one of the regions is of the form: Ae^{kx} If you substitute this into Schrodinger's...
18. ### Recommended Microcontrollers?

Default Recommended Microcontrollers? Hey guys, Im looking into designing something for a Uni project. What we have in mind is a "Home Automated System". What we are going to do is find a model house (perhaps a doll house) that resembles a real house and design a system that can remotely...
19. ### Bode Phase plot of a second order system

Hey guys. I need to know how to draw a Phase Bode plot of a Second order system. I understand and can draw the Gain(Magnitude) Bode plot, but I can't seem to get the grip of the Phase one. As far as I know there is an asymptote at 0^{o} at low frequencies and an asymptote at 180^{o} at...
20. ### Zero-Crossing Demodulation of FM signals

Hey guys, For school I have to study the zero-crossing demodulation method of reconstructing an FM signal. So far what I've been reading has been confusing me a bit and I have a few questions to ask: 1) How does a LP-filter act as a "time averager" for a train of impulses? 2) Does the...
21. ### Materials Needed for Analogue Communications

Hey guys, I'm a second year Electronics Engineering undergrad student and this semester I'm studying a subject called Communications Engineering 1, which is basically an introduction to Digital and Analogue Communications. I'm really stuck so far on the Analogue stuff because our lecture...
22. ### Basic Optics Question. (wave front)

Homework Statement E=Emax.sin(ωt-kx) describes the electric field of a monochromatic plane wave traveling in the x-direction. Verify that a plane which is perpendicular to the x-diretion and moves along the x-axis at the same speed as the wave is a wave front. Homework Equations...
23. ### Product rule with 3 variables

Thankyou very much. Yes, I was trying to find y' in terms of the other stuff. Previously, I had only learned the product rule for two variables.. like u'.v + u.v'.
24. ### Product rule with 3 variables

hey there, At the moment at school I'm doing Implicit Differentiation. If i had for Instence 2y'yx + 6x = 0 how can I use the product rule on the first step when there are 3 variables? Cheers- Andy
25. ### Help with physics grav force

I am a year 12 student so please bear with me - I could be horribly wrong. PS: this is my first post on this forum! You need to figure out the change in gravitational potential energy from the height you gave, to the surface of the earth. You need to know that the formula for for...