Search found 709 matches

by jmorgan3
Thu May 06, 2010 7:27 pm UTC
Forum: Science
Topic: public misconceptions
Replies: 1073
Views: 149963

Re: public misconceptions

Ok, I have not googled it yet, but what's the difference between a sound wave and a shock wave? (Oh, does a shock wave travel faster than sound?) I saw a slow mo video of a bomb explosion. Watching the shock wave propagate across the field was amazing. Only amplitude. The speed of sound in a substa...
by jmorgan3
Sun May 02, 2010 7:06 pm UTC
Forum: Science
Topic: Thermodynamics problem
Replies: 2
Views: 2030

Re: Thermodynamics problem

The change in entropy of bodies 2 and 3 when coming into thermal equilibrium will be \Delta S = \int_{T_{3i}}^{T_{2f}} \frac{C dT}{T} + \int_{T_{2i}}^{T_{2f}} \frac{C dT}{T} = C \ln \frac{T_{2f}^2}{T_{3i}T_{2i}} The change in entropy of body 1 must be equal to the combined entropy change in bodies ...
by jmorgan3
Sun Apr 25, 2010 2:03 am UTC
Forum: Science
Topic: Looking for a WAV Editor for Acoustics Research
Replies: 4
Views: 910

Re: Looking for a WAV Editor for Acoustics Research

Thanks, Dream. I'll look into those.
by jmorgan3
Fri Apr 23, 2010 4:00 pm UTC
Forum: Science
Topic: Looking for a WAV Editor for Acoustics Research
Replies: 4
Views: 910

Re: Looking for a WAV Editor for Acoustics Research

Thanks SWGLassPit. The problem with audacity is that it can't write wav files with more than 2 channels.
by jmorgan3
Fri Apr 23, 2010 2:28 pm UTC
Forum: Science
Topic: Looking for a WAV Editor for Acoustics Research
Replies: 4
Views: 910

Looking for a WAV Editor for Acoustics Research

I'm looking for a WAV editor for use at my co-op job to analyze recording of UAVs. Ideal features: -Free -Easy-to-Use FFT -Ability to Read\Write WAV Files with Multiple Channels of Audio (More than two) -Cross-correlation functions I appreciate any suggestions, even if they don't have all of these f...
by jmorgan3
Mon Apr 19, 2010 5:38 pm UTC
Forum: Science
Topic: EMP and Engines
Replies: 3
Views: 762

Re: EMP and Engines

According to this report, most modern cars will survive an EMP with no problems or only minor problems, due to their shielding against electromagnetic interference. I would imagine that even a General Aviation engine would have more shielding than a car, and would therefore be even more survivable.
by jmorgan3
Wed Apr 14, 2010 9:58 pm UTC
Forum: Science
Topic: About the speed of light
Replies: 17
Views: 1974

Re: About the speed of light

Vaporice wrote:But according to you all, what would happen would be that the pole would first be compressed, and later it would be expand again on the top of the pole? And this at the speed of sound?

This is exactly correct.
by jmorgan3
Tue Apr 13, 2010 6:14 am UTC
Forum: Science
Topic: Speed of Sound Humidity Dependent Formula
Replies: 1
Views: 643

Re: Speed of Sound Humidity Dependent Formula

Try "The variation of the specific heat ratio and the speed of in air with temperature, pressure, humidity, and CO2 concentration," Owen Cramer, The Journal of the Acoustical Society of America, 1993, p.2510.
by jmorgan3
Fri Apr 09, 2010 8:39 pm UTC
Forum: Science
Topic: Need help with a physics problem
Replies: 11
Views: 1631

Re: Need help with a physics problem

To make sure the units agreed in the equation, I multiplied 7.8 and 4 by 3600. Here's your problem. Don't just multiply things by whatever feels right. You need to figure it out with actual thought. For instance, 1 revolution/hour needs to be multiplied by something that has hours on the top and se...
by jmorgan3
Sun Apr 04, 2010 9:17 pm UTC
Forum: Science
Topic: Liquids lighter than water and Water Rockets
Replies: 8
Views: 4099

Re: Liquids lighter than water and Water Rockets

The mathematical model of a bottle rocket is, ironically, more complex than a chemical rocket, so the math and physics don't boil down to a convenient little equation like this . However, numerical methods work well for giving the delta-V of specific rockets. Playing around with the various constant...
by jmorgan3
Mon Mar 29, 2010 3:26 pm UTC
Forum: Science
Topic: Sources of Inspiration
Replies: 23
Views: 1994

Re: Sources of Inspiration

nehpest wrote:Deep dark secret: the movie Down Periscope is what tipped the scales in favor of engineering over pure science.

Care to explain this? I'm an engineer and I like the movie, but I can't think of a link between the two.
by jmorgan3
Sun Mar 28, 2010 6:17 pm UTC
Forum: School
Topic: Movies Featuring people with mental problems
Replies: 16
Views: 2448

Re: Movies Featuring people with mental problems

Batman. That guy has issues.
by jmorgan3
Thu Mar 25, 2010 9:13 pm UTC
Forum: Science
Topic: Integrating Distance vs. Time
Replies: 7
Views: 3227

Re: Integrating Distance vs. Time

hawkmp4 wrote:Divide the integral from some time a to some time b of distance wrt time by the length of time b-a, though, and you'll have something possibly useful.

Average position.
by jmorgan3
Sat Mar 20, 2010 6:06 am UTC
Forum: Science
Topic: Is a pack consciousness possible?
Replies: 50
Views: 4567

Re: Is a pack consciousness possible?

evilspoons wrote:What if another animal, constantly hunted by these pack creatures, evolved the ability to scream at precisely the pitch required to jam the pack ability?

Worse, imagine one of the pack members manipulating the rest to further its own reproductive success? An intraspecies predator?
by jmorgan3
Thu Mar 04, 2010 1:38 am UTC
Forum: Science
Topic: Arguing for the existence of chloroplasts
Replies: 22
Views: 2370

Re: Arguing for the existence of chloroplasts

Well, there are plenty of phototrophic prokaryotes that get by just fine with no chloroplasts, so in a way he was right, but not really, because eliminating chloroplasts wouldn't eliminate autotrophs. If you actually eliminated all photosynthesis, then life would pretty much go to shit, though. Org...
by jmorgan3
Mon Mar 01, 2010 10:00 pm UTC
Forum: Science
Topic: public misconceptions
Replies: 1073
Views: 149963

Re: public misconceptions

Would you, if the floor of the ship were sufficiently more dense than the walls and ceiling? You fall towards the center of mass of the vessel. However, this effect is negligibly weak. If you weigh 100 kg, and you're 10 meters away from a 100 metric ton mass center, the gravitational force is of or...
by jmorgan3
Fri Feb 26, 2010 3:16 am UTC
Forum: Science
Topic: Capacitor Charging Circuits
Replies: 3
Views: 1011

Re: Capacitor Charging Circuits

Correct. Make sure you don't apply more voltage than the cap is rated for.
by jmorgan3
Fri Feb 26, 2010 3:13 am UTC
Forum: Science
Topic: Funding from the military
Replies: 60
Views: 5179

Re: Funding from the military

May I ask what field?
by jmorgan3
Wed Feb 24, 2010 4:16 am UTC
Forum: Science
Topic: Chemistry-thermodynamics of reactions
Replies: 12
Views: 981

Re: Chemistry-thermodynamics of reactions

Yeah, you could think of it that way: it's kJ per mole of (2 H2O molecules) or kJ per mole of (1 CO2 molecule and two H2O molecules)
by jmorgan3
Wed Feb 24, 2010 3:37 am UTC
Forum: Science
Topic: Chemistry-thermodynamics of reactions
Replies: 12
Views: 981

Re: Chemistry-thermodynamics of reactions

joshz wrote:So it's essentially kJ/1 mol (all products, whatever their coefficients)?

I'm not sure what exactly you mean by this.
by jmorgan3
Wed Feb 24, 2010 3:18 am UTC
Forum: Science
Topic: Chemistry-thermodynamics of reactions
Replies: 12
Views: 981

Re: Chemistry-thermodynamics of reactions

Stop thinking about it in terms of heat per mole of water. That's not what delta-H is. delta-H is not a property of the reaction. It's a property of a particular chemical equation with certain coefficients. It's tempting to think of it as heat divided by moles of product, but that's not what delta-H...
by jmorgan3
Wed Feb 24, 2010 2:40 am UTC
Forum: Science
Topic: Chemistry-thermodynamics of reactions
Replies: 12
Views: 981

Re: Chemistry-thermodynamics of reactions

Think of it this way: multiplying all of the terms in that chemical equation by one mole gives you: 2 moles of H 2 + 1 mole of O 2 -> 2 moles H 2 O, with a delta-H of -572kJ. If you divided that equation by two, you would get 1 mole of H 2 + .5 moles of O 2 -> 1 mole H 2 O, with a delta-H of -572kJ/...
by jmorgan3
Fri Feb 19, 2010 6:56 pm UTC
Forum: Science
Topic: Stress Tensors and the static behaviour of Solids
Replies: 15
Views: 1689

Re: Stress Tensors and the static behaviour of Solids

As a plate-like structure instead of a truss, do you reckon it's going to be stronger? You mentioned the Eiffel Tower earlier. Do you think there's a reason Mr. Eiffel made it out of beams rather than panels? I'm not saying your goal is impossible with panels, just that it's probably not the most p...
by jmorgan3
Fri Feb 19, 2010 5:44 pm UTC
Forum: Science
Topic: Stress Tensors and the static behaviour of Solids
Replies: 15
Views: 1689

Re: Stress Tensors and the static behaviour of Solids

The equations I linked to only apply to plates that are loaded normal to the surface of the plate. That is not the case here. The way you are loading the plates in the drawing, you will have to worry about buckling, as Zamfir warned. I doubt you'll find any analytical solutions to the situation you'...
by jmorgan3
Thu Feb 18, 2010 6:47 pm UTC
Forum: Science
Topic: Stress Tensors and the static behaviour of Solids
Replies: 15
Views: 1689

Re: Stress Tensors and the static behaviour of Solids

My impression is that the sphere is being supported by the faces of the plates, rather than on the edges, where buckling would be a factor. Regardless, the OP isn't designing a satellite for actual use; he is designing it for a class which, apparently, doesn't include structures as part of the curri...
by jmorgan3
Thu Feb 18, 2010 6:08 pm UTC
Forum: Science
Topic: Stress Tensors and the static behaviour of Solids
Replies: 15
Views: 1689

Re: Stress Tensors and the static behaviour of Solids

I'd steer away from FEA unless you're only using it for very very basic analysis From the sound of it, that seems to be exactly what he's doing here. If I were he, I would model the geometry (pretty simple, judging by his description), then set up simple constraints (e.g. these 8 points are fixed b...
by jmorgan3
Thu Feb 18, 2010 1:18 am UTC
Forum: Science
Topic: Stress Tensors and the static behaviour of Solids
Replies: 15
Views: 1689

Re: Stress Tensors and the static behaviour of Solids

Well, I got one of those and it goes into beams a lot but not much on plates. I essentially have a cuboid satallite, with a four-sided pyramid on the bottom with a spherical fuel tank suspended in the middle. Suspended how? There are some analytical solutions for flat plate deflection, mostly for r...
by jmorgan3
Thu Feb 11, 2010 11:36 pm UTC
Forum: Science
Topic: Flux
Replies: 18
Views: 1406

Re: Flux

Basically, he's saying that the flux through a certain area (dA) is equal to that area times the field going through it (E dA) This only holds if the electric field is perpendicular to the surface. If it's not, you have to take that into account. It's still not very difficult, though, so I don't kn...
by jmorgan3
Fri Jan 29, 2010 9:42 pm UTC
Forum: Science
Topic: Thrust generated by pressurized air
Replies: 13
Views: 4861

Re: Thrust generated by pressurized air

Okay, by the sound of it, you're talking about a fairly low-velocity airstream (less than a couple hundred mph), right ? If that's the case, then you can assume incompressible flow and just use Bernoulli's equation.
by jmorgan3
Fri Jan 29, 2010 2:48 am UTC
Forum: Science
Topic: Thrust generated by pressurized air
Replies: 13
Views: 4861

Re: Thrust generated by pressurized air

This is the equation you want: http://en.wikipedia.org/wiki/Rocket_engine#Net_thrust. Note that Pe and Ve both depend on the geometry of the nozzle and you need a good bit of bit of college-level thermodynamics to figure out what they'll be.
by jmorgan3
Fri Jan 08, 2010 8:52 pm UTC
Forum: Science
Topic: Physics motion question
Replies: 6
Views: 1261

Re: Physics motion question

Secateurs wrote:I then found the distance the second camel travels while accelerating (11.69512 m)

Check this.
by jmorgan3
Wed Jan 06, 2010 7:50 am UTC
Forum: Science
Topic: why would a photon drive suck so bad ?
Replies: 29
Views: 5826

Re: why would a photon drive suck so bad ?

Carnildo has a good point- there is always a trade-off between mass required and energy required. Electric rockets are a way to sacrifice the kind of "efficiency" I discussed in favor of using less mass. These vehicles can afford to sacrifice energy-efficiency because their solar panels ar...
by jmorgan3
Wed Jan 06, 2010 3:52 am UTC
Forum: Science
Topic: why would a photon drive suck so bad ?
Replies: 29
Views: 5826

Re: why would a photon drive suck so bad ?

The purpose of a drive is to change the momentum of the vehicle, while the cost of operating the drive is the energy of the propellant stream. Therefore, one measure we can make of the "goodness" of a drive is the amount of momentum change you get divided by the energy it costs you. Let's ...
by jmorgan3
Mon Jan 04, 2010 12:40 am UTC
Forum: Science
Topic: Heat and Ideal Gases
Replies: 10
Views: 1250

Re: Heat and Ideal Gases

I want to heat from 0 C to 140 C, keeping it at a constant temperature How does this work? Perhaps it was a mistype and they meant constant pressure instead. Well, theoretically, molar specific heat at constant pressure is 5/2 * R for a monoatomic gas, so the answer in that case is 3 moles * (5/2) ...
by jmorgan3
Sun Jan 03, 2010 8:50 am UTC
Forum: Science
Topic: Heat and Ideal Gases
Replies: 10
Views: 1250

Re: Heat and Ideal Gases

So let's say I have a certain amount of a monatomic ideal gas (three moles, to be exact) which I want to heat from 0 C to 140 C, keeping it at a constant temperature. How much energy (in joules) would I need to use to produce such a temeperature change? More importantly, is it even possible to calc...
by jmorgan3
Sun Jan 03, 2010 4:34 am UTC
Forum: Science
Topic: Heat and Ideal Gases
Replies: 10
Views: 1250

Re: Heat and Ideal Gases

Ethliel wrote:I want to heat from 0 C to 140 C, keeping it at a constant temperature

How does this work?
by jmorgan3
Sat Jan 02, 2010 5:20 am UTC
Forum: Science
Topic: Optimal Rocket Trajectory
Replies: 6
Views: 1007

Re: Optimal Rocket Trajectory

design the whole vehicle for the highest maximum value of C L 1/2 /C D where C L is lift coefficient and C D is drag coefficient. ESPLAIN! The range equation for rockets and jet engines and any other method of propulsion where thrust is proportional to fuel consumption is http://upload.wikimedia.or...
by jmorgan3
Sat Jan 02, 2010 4:33 am UTC
Forum: Science
Topic: Optimal Rocket Trajectory
Replies: 6
Views: 1007

Re: Optimal Rocket Trajectory

I'll get the smart-ass answer (smart ass-answer?) out of the way: accelerate to orbital velocity, then let the rocket cover as much horizontal distance as you want it to, and de-orbit it. This requires a delta-V of twice orbital velocity, though. For a flat earth and realistic aerodynamics, you'd wa...
by jmorgan3
Thu Dec 31, 2009 8:09 pm UTC
Forum: Science
Topic: Aperture Science Hand-held Portal Device Related Physic Quiz
Replies: 19
Views: 2968

Re: Aperture Science Hand-held Portal Device Related Physic Quiz

7. You have a sealed box containing two portals (each on one of the six interior faces) and a lit lightbulb. Figure out which sides of the box the two portals are on. You can't open the box. Measure the temperature of each wall. The coolest walls are the ones with portals on them, because the porta...
by jmorgan3
Thu Dec 31, 2009 11:57 am UTC
Forum: Science
Topic: Aperture Science Hand-held Portal Device Related Physic Quiz
Replies: 19
Views: 2968

Re: Aperture Science Hand-held Portal Device Related Physic Quiz

8. You are a mad scientist. You note that Venus has too much atmosphere and Mars has too little for humans. You wish to fix this by shooting one portal at Venus and one at Mars. Assuming you can see both planets in the night's sky, in-transit portals travel at c, and a connected portal has cross-se...

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