# Search results

1. ### Biochem practice exam help - Test tomorrow

Hi all. I have a biochem test tomorrow, and would like some help. I went through the practice exam that was given to us, and from past experience the real test and practice test tend to be very similar. Also, from past experience, I tend to get a couple of them wrong because I believe that I...

Bump?
3. ### Linear Algebra: 4 Fundamental Subspaces

Homework Statement Without computing A, find the bases for the 4 fundamental subspaces. [1 0 0][1 2 3 4] [6 1 0][0 1 2 3]=A=LU [9 8 1][0 0 1 2] Homework Equations N/A The Attempt at a Solution There was an "example" in the book. It just showed the answers. It was: [1 0...
4. ### Simple Linear Algebra question

I have to do a LDL^{T} transform of a symmetrical matrix: [2 -1 0] [-1 2 -1] [0 -1 2] And, I'm just wondering if I have to do a row exchange, or something. I can't remember if the L matrix has to have the form [x 0 0] [x x 0] [x x x] where the x's are nonzero numbers...
5. ### Friction: Block on Ramp

So now I get x-direction Fx = N sin() - mu N cos() ax = [N sin() - mu N cos()]/m T = -[v0x cos() m]/[N sin() - mu N cos()] Substitute N = mg cos() T = -[v0x cos() m]/[mg cos() sin() - mu mg cos() cos()] cancel m cos() to arrive at original answer, right? Thanks for all of your...
6. ### Friction: Block on Ramp

How is it the -x-axis? Although, I now see that you're saying that the normal is theta from the positive y-axis, and needs to be sin(theta), right?
7. ### Friction: Block on Ramp

wrt the ramp 90º or wrt x-axis 90º+theta How is the angle not wrt the x-axis? It's the angle made by the ramp with the x-axis
8. ### Friction: Block on Ramp

No? I always thought that if it was an x component it was cosine, and y component was sine. Those are both the x components, so...
9. ### Friction: Block on Ramp

For part a, I got T = -v0/(g sin(theta) - mu g cos(theta)] Obviously since it's the same situation, I should be able to get the same answer for part b, But I'm having difficulty. x-direction Fx = N cos() - mu N cos() ax = [N cos() - mu N cos()]/m T = -[v0x cos() m]/[N cos() - mu N cos()]...
10. ### Friction: Block on Ramp

Excellent. Thank you. For the second part, with the axes being the vertical and horizontal, I'm going to have a multi-component acceleration, yeah? In the y-direction, the forces working is the weight/gravity which is pointing in the -y-direction, and components of the Normal and Friction...
11. ### Friction: Block on Ramp

N = mg cos(theta) So, a = g sin(theta) - mu g cos(theta)? Then, v = v_0 +at Since we're looking at when it comes to rest, v=0 T = -v_0/a Look right?
12. ### Friction: Block on Ramp

I did draw a diagram. F = mu N yeah?
13. ### Friction: Block on Ramp

Homework Statement A block slides down a slope from point O with initial speed V. THe sliding coefficient, mu, brings the block to rest at time T. Using the ramp as the x-axis and the perpendicular as the y-axis, find T. Homework Equations F = ma mu = mg sin(theta) a=dv/dt The...
14. ### OPTICS - Final tomorrow - Practice test help

WVU And apparently, if you only have 3 characters in a message, it's "too short"
15. ### OPTICS - Final tomorrow - Practice test help

Homework Statement Homework Equations The Attempt at a Solution (3) I haven't been able to start this one at all. (6) I got part a (+45º P-state). I tried to do b and I got [1+i, -i+1] which isn't a polarization state, so I'm not sure what to do with c or if there is some...
16. ### Optics - Diffraction

I did get it. Thank you to the both of you.
17. ### Optics - Diffraction

If that end part is true, then what I already did is correct, I just forgot to divide the arguments of the sine and exponential by 2.
18. ### Optics - Diffraction

I don't understand where the exp(ik) is coming from. And, by phase, do you mean phase shift. If that's the case, it doesn't effect it at all. E is the aplitude of the wave, and it doesn't depend on the phase as far as I can remember.
19. ### Optics - Diffraction

I used the right identity then, I just forgot to divide by 2. Because if you check the definition of delta in the problem statement, it's divided by 2R. I just don't know how to get rid of that extra exponential term. Also, I did a little thinking and thought that L'Hopital was the way to go...
20. ### Optics - Diffraction

I'm not sure how to get the exponentials into a sine function. Because exp(ix) = cos(x)-isin(x) and that doesn't seem to help me. I thought that exp(ix)-1=2i exp(ix) sin(x). Is that not right? As for (d), it was just the wording of the problem. It doesn't ask for the limit, but if no one can...
21. ### Optics - Diffraction

I'm bumping this because I finished parts (a) and (b), but now I'm having trouble with (c). I know that the irradiance is energy/area/time. But, I never understood how to derive it. The only equation our book (Hecht) has in it that defines irradiance is the time average of the poynting...
22. ### Optics - Diffraction

[SOLVED] Optics - Diffraction Hi. I was given an extra credit problem in class to derive equations related to multiple slit diffraction. I was wondering if someone wouldn't mind looking over what I have so far, and pointing me in the next direction. Thank you! Homework Statement Homework...
23. ### Optics exam tomorrow, need help please

I did indeed get the same answer; although, it took a few tries with that apparent depth method. Thank you very much.
24. ### Optics exam tomorrow, need help please

Are you referring to (n1/so)+(n2/si)=(n2-n1)/R? My initial thought about this problem was to use that equation, but I wasn't sure what to do about R. I didn't think about setting it to infinity. Thank you.
25. ### Optics exam tomorrow, need help please

Thank you again for the reply. A couple clarifications to make sure I understand. So the ray I draw from the fish is arbitrary and I just choose a random angle, and use that angle in Snell's law to calculate the refracted angle? Also, which line is the apparent depth? The entire line made...
26. ### Optics exam tomorrow, need help please

Thank you for the reply. It did ask to locate the image of the fish, sorry. I don't understand how to determine the apparent depth. We were never given anything like this problem in lecture or in homework. Could you explain that a little more in depth please?
27. ### Optics exam tomorrow, need help please

Hello, first time poster. I'm in an optics class because I thought it would be fun, but I'm having a terrible time. And I didn't do so well on the first test. The second test is tomorrow and I want to do well on it. We were given a practice exam with 3 questions. I got two of them, but the third...