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Ask a Scientist

Discussion in 'Permanent Threads' started by mekka, Oct 20, 2009.

  1. scootah

    scootah
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    I went to google and searched for 'how does the internet work' and the first link that came up was a pretty good guide. Then I went to Wikipedia and searched for 'Data Compression' and miraculously - the answer appeared. Probably the best documented and most easily found information on the internet is how the internet works - and data compression is a fundamental part of that.

    I just feel silly for having been trolled now.
     
  2. Black Sheep Dog

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    This is a weird question, but does anyone know if there is any science behind couples who can consistently cum at the same time while having intercourse? I figured it has something to do with increasing the chance of fertilization.
     
  3. whathasbeenseen

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    Kegels?
     
  4. Kubla Kahn

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    I dont know man, if the statistics are right, most women aint cumming. Yet still a whole lot of them get knocked up.
     
  5. BrianH

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    Read that ol' classic "Sperm Wars." Yes, orgasm greatly increases the chances of fertilization because it allows sperm to travel through the cervix unimpeded by cervical mucus.
     
  6. Black Sheep Dog

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    Taking it further, I was wondering if it is possible that a woman's body figures out when a guy is going to cum and responds by synchronizing with him or something like that. My last girlfriend used to cum at the same time as me, like 50% of the time, and I thought it was really weird. Then again, I suppose it's possible that she just faked it.
     
  7. PewPewPow

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    Kind of a basic physics question but it's kicking my ass.

    An 86kg astronaut applies a pushing force of 105N to a 645kg satellite over a period of .510 seconds. How far away are the satellite and astronaut from each other in 78seconds? Note: 78seconds from when the astronaut begins his pushing motion.

    So since this is happening in space I assume no friction or gravity playing a role. I got the acceleration of the astronaut by using F=ma and used Newton's third law to state that the satellite is also applying a force of 105N.
    Thus the acceleration of astronaut is 1.22m/s^2 and the acceleration of satellite is .16 m/s^2

    Here's where I'm having trouble. Should I use the kinematic equation X - Xo = Vot + .5at2
    for the first .51 seconds and then get the velocity from that and use the equation again with T= 77.49 seconds with Vo being what I got in the first equation?
     
  8. Nettdata

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    Why is it that when I have a hot coffee or some other hot drink, and I stir it in a mug, and begin to tap the rim of the mug with a spoon repeatedly, the resultant sound increases in pitch?
     
  9. zwtipp05

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    This looks like a momentum problem.

    You can set up an equation for conservation of momentum and another for conservation of energy to solve for the velocities.

    Assume both are at rest next to each other. Then the change in momentum is equal to the impulse (F*dt). Once you have those 2 equations, you can solve for the velocities, then its just a matter of finding the distances using your kinematics equations.
     
  10. scootah

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    When vibrations occur at different frequencies, the sound that you hear changes. The way that an object vibrates is what determines the frequency of the sound wave. If you take an empty glass and ding it with a spoon - you have the default wave. If you alter the way the glass responds to impact, changing the suspension properties - you change the frequency of the wave that will result from dinging the glass. Cushioning the glass in your hand, adding different amounts of water, or adding a liquid in motion will change the way the container will vibrate as you ding it with the spoon. When the vibration alters - the wave frequency alters.

    This bit is just me guessing - but I think that when the fluid contained within the container is in motion (IE you're actively stirring it) - the sound will presumably get deeper as the force of the spoon impact is diffused by the fluid motion so the container vibrates more slowly. As the liquid motion slows - the diffusion of the impact of the spoon will diminish - so as you take the spoon out out of the cup, the spin slows, the diffusion reduces and the container vibrates more effectively so you hear the pitch rising as you continue to tap on the rim.

    Or maybe you're just not aware of the fact that your changing the way you tap and you're manipulating the results with unconscious bias.
     
  11. gocougs750

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    *I posted this in another thread but I thought this may be a better thread. Remove if necessary.

    I am not sure what to do in this problem. We are supposed to solve with cylindrical coordinates but i think the only way to do that is with trigonometric substitution. Even when I do this I keep getting the wrong answer.

    It is supposed to equal

    {4pi(2^.5 -1)}/3

    anyone know how to go about this?
     

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  12. selective misogyny

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    I don't think it's the force of impact that is diffused by the fluid. Here's my take on it: It's a compressive-expansive interaction. Say you hit the spoon on the cup. The instant after, the cup compresses in one direction and expands in another (becomes VERY SLIGHTLY oval-shaped). The instant after that, the cup expands in the direction it was previously compressed and compresses in the region it was previously expanded. This cycle continues until most of the energy is transferred to air pressure disturbances (sound) and the rest is lost to the motherfucker of all energy transfer processes (friction/entropy). Now if the fluid isn't moving, this compression/expansion interaction is happening to the same particles in the fluid throughout its entire life cycle, so the fluid has the same "rebound" effect as the cup (although the mechanism for rebound in the fluid is compressibility whereas in the cup it's stress). The synchronization between fluid and cup motion in the stationary fluid case allows the cup to vibrate more efficiently and thus produce a higher frequency of vibration (higher pitch of sound). But if the fluid is rotating, the fluid acts as a dampener to the speed of vibration since fluid areas that did not feel compression yet are moving into cup areas that are trying to compress, thus slowing the cup's compression process down. Same process except opposite direction for the expanding regions.

    I'm pretty sure that's what's happening, although I'm more of a fluids guy than a structural vibration guy so my take on the deformation of the cup might be slightly off. Even if it is though, the mechanism for slowing the frequency of vibration should still be the same.

    By the way, how retarded is it that I'm procrastinating from doing fluids homework by answering a fluids question on the internet?
     
  13. Nettdata

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    Interesting.

    Study on how cats drink.

    <a class="postlink" href="http://www.nytimes.com/2010/11/12/science/12cats.html?_r=1" onclick="window.open(this.href);return false;">http://www.nytimes.com/2010/11/12/scien ... .html?_r=1</a>



    Thus proving that cats are smarter than dogs as they know science and shit.
     

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  14. Queen-Bee

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    That's the same way they suck out a baby's soul.
     
  15. scootah

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    I understand that when calculating impact force, it's force=mass*acceleration - but I'm trying to get my head around the math behind the difference between hitting someone with say a strip of suede leather, and a baseball bat. I understand that the increased mass of the baseball bat means greater force, but does the material rigidity play a role? Is there a diffusal of force based on the compression characteristics of the impacting object? How do I calculate or express that?

    Conversation comes from someone claiming that they were struck roughly in the area of the kidneys with a leather flogger, and that this event caused enough kidney damage to have multiple cases of DVT as a result. I'm trying to explain my firmly held belief that without a massive pre-existing kidney condition - there's no fucking way. There's just not enough fucking mass in a leather flogger to do that kind of damage - and I have the suspicion that a suede flogger just wouldn't transfer force effectively enough to damage someone's kidneys like that unless they carved a hole to expose your kidney and they were beating the organ directly.
     
  16. Spoz

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    At impact, a flexible object will deform significantly more than a stiff object, and this deformation is work. To do work, requires energy; energy that is not going into the impacted objects kidneys. There won't be an easy way to theoretically derive the formula for exactly how much work is done, but my guess is not much at all. My understanding is that given the same mass and contact area, the force transferred to a person would be nearly identical for a rigid or flexible object (the difference being the energy used for deformation which ends up as heat, assuming both objects come to a complete stop).

    One factor that may account for a higher energy impact from a flexible object would be a slingshot like effect of the flexible object. If someone was to take a flogger and attempt to flog someone as hard as they can, they intuitively know how to swing it for maximum impact force (you have to love the human brain). I think you'll find that to accomplish this, they not only move the flogger towards the impact site, but also swing it in such a way that the impact velocity is much higher (in the same mechanism as nunchaku or a trebuchet). Even though there is a maximum speed a person can move their arms, a flexible object allows that slingshot-like effect to increase the impact velocity and hence impact force.
     
  17. Racer-X

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    The biggest difference between a strike with a flexible object and a rigid one is in the acceleration portion of f=ma. The rigid object stops all at once so the acceleration is high. A flexible object takes longer to stop because it deflects around the target. Depending on the flexibility of the striker it's probably easier to think about it as a chain of masses hitting over a certain time but as each mass stops, it acts to slow down the next mass which lessens the acceleration. I don't know if that's clear at all but I hope it makes some sense.

    You also get force distributed over a larger area with a flexible object because it tends to conform to the target; this isn't as important if you're hitting a soft target like a human body because the soft target will deform and act to spread the force.
     
  18. Disgustipated

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    I'm no scientist, but I know a bit about hitting people with things. So, correct me if I'm wrong and forgive the lack of technical explanation.

    Force = Mass x Acceleration is correct, but that's practising physics in a vacuum. There's also issues of drag, surface area of the hit, rigidity of the implement and recoil. These will all affect the impact.

    Because we're swinging in air, there's drag on the implement. This will affect the flogger more than the bat because of its inherent lack of rigidity. To some extent, this is overcome by the summation of force/kinetic linking that can be used on the flogger (as discussed above).

    Surface area of the hit is relevant and recoil are relevant as the potential energy of the swung implement must be transferred at the point of impact. Whatever the force is at that point primarily goes in two directions; into the target and back through the implement. The force going into the target is spread over the area contacted (think Psi - pounds per square inch). It's the same theory as looking at a spike versus a brick; if you push the spike just hard enough to puncture an object and then apply the same force with a brick, it won't puncture. The spike concentrates the same amount of force into a smaller area. Because of the nature of the implements, even though the bat is probably bigger overall its point of contact is likely to be smaller than the flogger (because it spreads out); so all other things being equal the bat will transfer the force of the hit over a smaller surface area.

    An amount of the force comes back through the implement in recoil. The bat is rigid, so you feel it more in your hands. The flogger is loose, and you don't feel the impact as much. What's actually happening is the bat is transferring more energy into the target, because its rigidity and the fact that you're holding it means that it can only go that way. The flogger, being loose, allows for a portion of the force to dissipate through the "relaxation" of it at point of contact.

    In terms of DVT, I agree that without some predisposition it is unlikely the flogger could cause DVT. A flogger will sting the surface but generally not penetrate to any great degree and the human body has establish some deep layers to hide the kidneys. I could be wrong, but I think I would need to flog someone to the point where I'm digging chunks out of their back to do that kind of damage.
     
  19. Whatthe...

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    Is there anybody on here who is a chemical/mechanical engineer with any evaporator/distillation knowledge. I'm having a problem with a process I've designed and I can't figure it out for the life of me.

    I have a flash tank with a rotary lobe blower drawing the steam out of it. The temperature of the water in the bottom of the tank is 82 DegC. Turn on the blower and the vacuum rises to 10.5"hg and the water starts to boil. This is exactly what I expect to happen. The vacuum generated by the blower is tied to the temperature of the water. When I turn on the blower with the water temperature at 86 Deg C, the vacuum goes to 8.5"hg. My problem is the blower is becoming overloaded and tripping the motor protection. The overload starts at around 600rpm and the blower trips off at 1100rpm. Design requires 2143 rpm.

    I can't figure out why the blower keeps tripping off. The blower is a constant volume device. I don't think I have a flow problem because if I wasn't evaporating water fast enough to feed the blower the vacuum would keep increasing until the enough water was boiling to keep up with the demand of the blower. If I run the blower open to atmosphere, I don't have any problems.

    Any thoughts?
     
  20. MrPrime

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    First thought on it seems that your blower (more specifically the motor) might be too small for the job. It sounds like it doesn't have enough balls to to get and sustain the vacuum you require, then it stalls out and blows the breaker.