# Search results for query: *

1. ### Does the derivative of a P(V) eqn give the eqn for change in Pressure?

So it would be rate of change with respect to volume?
2. ### How to calculate initial pressure and temperature - adiabatic process

So I use final volume and pressure for this? I treid that and it didnt give the right answer for me.

4. ### Does the derivative of a P(V) eqn give the eqn for change in Pressure?

Gives rate of change. For instance, if you take the derivative of velocity, you get acceleration, which is the rate of change of velocity.
5. ### Does the derivative of a P(V) eqn give the eqn for change in Pressure?

I know the integral of a P(V) eqn gives an eqn for work. I was wondering if taking the derivative of a P(V) eqn gives an eqn for change in pressure?
6. ### How to calculate initial pressure and temperature - adiabatic process

Im confused on working backwards so to speak to find adiabatic work. To find work for this adiabatic process, I either need to know the change in temperature OR the initial pressure (I think?). The issue is that I don't know either the initial temperature nor the initial pressure so I am not...
7. ### Fish Reflection: Analyzing Light's Interactions with Water

You know what, after thinking about it and reading it a few more times I think I know what it means. The fish 3.5 m above the mirror. The fish is also 3.5 m deep. So the mirror is actually 7m deep. Very poorly worded question. Since the mirror is underneath, I can find the location of the...
8. ### Calculate change in entropy per minute.

For the ice at 273.15 K, its being heated up (dQ/dt is positive). where here dQ/dt is per min (not second) DeltaS=dQ/dt/T=3910000/273.15 = 14314 For the steam at 373.15, its being cooled down (dQ/dt is NEGATIVE) -3910000/373.15 = -10478 Add them up and I get a total change of 3836... close...
9. ### Calculate change in entropy per minute.

The heat absorbed by the ice-water mixture is the heat emitted by the steam-water mixture. I divided it by temperature because that gives the right units and is consistent with the equation Q=T*change in entropy I suppose I need to find the temperature of the interphase maybe instead? Here...
10. ### Calculate change in entropy per minute.

So what I did was find the change in Q per min. Mass melted per min * latent heat capacity = Q per min = 11.5 kg /min * 3.4*10^5 J/kg = 3910000 J/min Now the equilibrium temperature is 100 degrees Celsius or 373.15 degrees kelvin. If I do 3910000 J/min / 373.15 K I get 10478 J/(K*min). This...
11. ### Fish Reflection: Analyzing Light's Interactions with Water

So let's pretend there was a person right above the water looking down and I wanted to find how deep the reflection of the fish appeared to be to the person. Is that when I would use n1/p+n2/q=(n2-n1)/R where n2 is 1.29 and p=3.5?
12. ### Fish Reflection: Analyzing Light's Interactions with Water

The way I read "3.5m above" was above the water since why else would refractive indexes even be given? If we assume its 3.5 above the fish, then 1/q+1/p=-2/R, where p=3.5m and R=6.2m This does indeed give -1.644 m or 1.644 m behind the mirror. What a dumb question. Who knows what the right...
13. ### Fish Reflection: Analyzing Light's Interactions with Water

i think this is where I am confused. The light is coming from the fish. but then it needs to come back to the fish for the fish to see itself. First light comes off fish and hits water. Then light travels through air and hits mirror. Then light goes back through air and hits water. Then goes...
14. ### Solving Destructive Interference: Angle vs Wavelength

i see, I was using a double slit eqn instead of a single slit. Looking at your link, tanx=x=y/D. So i don't know what y is nor d. d=y/x=y/0.108 = 9.2593y Now I can use y=(m*wavelength*D)/a to find width. m i assume is 2 because second angle measurement... 0.108d=(2*539 nm *d)/a a=9981.4815...
15. ### Fish Reflection: Analyzing Light's Interactions with Water

So first I looked at where the image of the fish appeared to be when it went through the water surface. since we can assume the water is flat, R is infinity, so n1/p=-n2/q. plugging in the values (n1=1.29, n2=1, p=3.5) I get q=-0.3686. So the image of the fish appears at 0.369 above the...
16. ### Solving Destructive Interference: Angle vs Wavelength

The destructive interference equation for small angles is angle=wavelength/(2a), where a is the width. I assume it means destructive interference since its talking about areas where no light is present. Using the equation after changing degrees into radians I get the answer of 2491 nm when the...
17. ### Oscillating spring experiment uncertainty

Then why is the term used?
18. ### Oscillating spring experiment uncertainty

Im confused by the statement of an "absolute certainty" here. Dont all uncertainties have a certain confidence to them? Ex. A 99% confidence interval will provide a much wider uncertainty than a 95% confidence interval? Isnt the uncertainty also dependent on the confidence interval you pick...
19. ### Lorentz Velocity Addition Problem

But if I do both numerator/denominator u'=u, which isn't the right answer.
20. ### Lorentz Velocity Addition Problem

How does it work then? I've determined the x-component of the velocity to be 2.7784E8 using ux'=(ux-v)/(1-(ux*v)/c^2) where I defined the variables in the same manner. i believe my answer is correct, though I have no way of veryfying. An earlier comment said I needed to find the x-component...
21. ### Lorentz Velocity Addition Problem

u'=u/(δ(1-(uv)/c^2) u' is the velocity of the object according to the individual moving at velocity v. u is the velocity of the object according the the individual in the rest frame. The question is asking for u`', the velocity of the object according to the individual moving at velocity v...
22. ### Lorentz Velocity Addition Problem

Why would I need to do x component first? Couldnt i just ignore x component and do y component since that's what the question is asking?
23. ### Lorentz Velocity Addition Problem

Its asking for the y component, which is j hat. The particle has a y-component velocity while the moving observer does not.
24. ### Lorentz Velocity Addition Problem

So for the formula, u'=u/(δ(1-(uv)/c^2) u=2.06E8 and v=0. I am only looking at the y components here. Since v=0 it really becomes u'=u/δ or u'= u*sqrt(1-(u^2)/c^2)). Anyways when I plug this in I am getting 1.49E8 when the answer should be 0.951E8. Am I not using the correct formula here?
25. ### Lens with different refraction index on each side

ya I am dumb. 1.3-1 isn't the same as 1.3-0. I get q = -60.88 when I use 0.3, so 60.88 above the water. Thanks.
26. ### Lens with different refraction index on each side

n1/p+n2/q=-(n2-n1)/R is this formula incorrect here?
27. ### Lens with different refraction index on each side

The rest is correct then? Shouldn't it be on top according to the formula?
28. ### Lens with different refraction index on each side

So I am not really familiar with lens questions when there's 2 different refraction indexes. I tried using n1/p+n2/q=-(n2-n1)/R but it doesn't seem to work. p would be the actual location of the fly and q would be the virtual location, what the fish sees if I am understanding correctly. n1...
29. ### Doppler question - find the observed frequency

How would one calculate the final velocity then if distance of the drop isn't given?
30. ### Doppler question - find the observed frequency

So first I calculate the final velocity by multiplying the time by the acceleration, 9.8, to get 88.2 m/s. Now I use the equation. (343/(343-(-88.2))*108.3 = 86.1477. But the answer should be 88.47. What am I doing wrong here?
31. ### Dampening force - find decrease in amplitude

So first I tried to find b. 0.454=(0.6)e^((-b/(2*11.6)*50) Anyways with some natural log algebra etc. I get b = 0.129378 But when I plug this into the same equation only changing mass to 17.7 kg I get 0.4998 or 50% when the answer should be 59.6%?
32. ### Harmonic motion - Find the Mass held between two Springs

Isnt E=kA^2=m(wA)^2 for two springs? For one spring it would be E=(1/2)kA^2=(1/2)m(wA)^2 right?
33. ### Harmonic motion - Find the Mass held between two Springs

But the question gives amplitude? Kinetic E of a spring would be (1/2)kx^2.
34. ### Harmonic motion - Find the Mass held between two Springs

So first I find the energy using the eqn (1/2)kA^2. Since there are two springs with the same k I multiply it by two to get kA^2. Energy I get is 2.0475, Now I use E=(1/2)m(wA)^2 to find mass. Again since there are two springs I use E=m(wA)^2. m=E/(wA)^2. w=(2(pi))/T btw. I get the answer of...
35. ### Compton Scattering - Find x component of electron momentum

I mean I thought I understood it since I was able to use momentum or energy to solve the problem you cite in that thread. The issue here is I don't have the final wavelength so nothing seems to work. Units are what I use as a last resort and don't always help. Trying to cancel them out units to...
36. ### Compton Scattering - Find x component of electron momentum

So I can find the initial momentum using p=h/wave = 4.98 x 10-23. Now my problem is that I don't know the final momentum of the photon nor electron, I just know the photon is scattered at an angle of 34 degrees. I know how to solve this problem if I was given the final wavelength of the light...
37. ### Compton Scattering - determine momentum

So either I need to find the angle the electron is ejected or the y component of its momentum. The y component of the photons momentum is sin(89.422)*4.872 x 10-23 = 4.872 x 10-23. The initial y component of the lights momentum is 0. Therefore the y component of the electrons momentum is -4.872...
38. ### Compton Scattering - determine momentum

so 0.59161 x 10-22 = cos(89.422) * magnitude light momentum + x component of electron momentum So I really now just need to find the magnitude of light momentum after scattering occurs. The scattered light wavelength ss 13.6 x 10-12, p=h/wavelength gives 4.8721 x 10-23. Using the above...
39. ### Compton Scattering - determine momentum

Ok so I used the formula change in wavelength = (h/mc)(1-cos(angle) to get an angle of 89.422 degrees, but isn't this giving the angle the photon is scattered and not the angle the electron is scattered? I could understand how I could use this vector to for lights momentum, but i don't see...
40. ### Compton Scattering - determine momentum

But the question doesn't give vectors, so how am I suppose to draw a vector diagram or assign vectors if none are known? y=yocto or 10-24.
41. ### Compton Scattering - determine momentum

So the initial wavelength gives the total momentum, p=h/11.2p. Which is 59.161y. Then I tried to substract the momentum from the scattered light to get the momentum of the electron. 59.161y-h/13.6p, which ends up being 0.4872 as the final answer, but the answer is supposed to be 0.77?
42. ### Calculating the waste heat of Carnot engine

Qin=W/e so e=1-Qout/(W/e) e=1-eQout/W 1-e=eQout/W (1-e)W/e = Qout (1-0.35481)*3560/0.35481 Youre right, must have messed up my algebra somewhere because this gives the right answer. Thanks.
43. ### Calculating the waste heat of Carnot engine

The answer is 6470 J. So since I have the two temperatures I could calculate the efficiency. First I convert to kelvin then get an efficiency of 0.35481. Now I can use e=W/Qin to get Qin. I get a value of 10033.54J. Now I can use e=(Qin-Qout)/Qout to get Qout, the waste heat. I get 7405.9 J...
44. ### Efficiency of heat engine question

Okay I finally figured out how to do but would really appreciate if you could explain why it works and why my earlier method was wrong (I hate this chapter so much). As you said, I calculated Q using nc(T change). Did this for each step. Some Qs were negative, some were positive. Now I then...
45. ### Efficiency of heat engine question

It would be the sum of the work minus the sum of the heat. Idk if its because I am calculating it wrong or not, but I get 0. But this seems to be wrong because if the internal energy didnt change, doesn't that mean the efficiency was 100%?
46. ### Efficiency of heat engine question

Okay so I think I've gotten somewhere but I am not sure how to use heat to get work. What I did for each temperature changes was use the equation Q=nc(T change). the c is either (3/2)R or (5/2) R depending on if its isochoric or isobaric. Now I have all the Qs, some positive, some negative. The...
47. ### Efficiency of heat engine question

What do you mean by set them equal? I could try to simplify my equation above to get (R(change T1 + change T2))/(-cv(change T1) - cp (change T2)) but i don't think its right.
48. ### Efficiency of heat engine question

I think the bottom signs need a negative? Just looking at the graph I know that Pi can't be Pf (they have different height). The problem with PV=nRT is that I don't know n. Or P. Or V. But let's say I substitute change in T into the equation everywhere. Pi(nR(change T)/P) + Pf(nR(change T)/P)...
49. ### Efficiency of heat engine question

So efficiency is W/Qin. W= 0 for isochoric processes and for the isobaric, P(change in V). So W=Pi(Vi-Vf)+Pf(Vi-Vf) Qin is negative Qs.This would happen at step 2 and 3. For the isobaric, Q=ncv(change in T) and for isochoric, Q=ncp(change in T). Now if I put everything in the equation I get...