What is Shock: Definition and 237 Discussions

In physics, a shock wave (also spelled shockwave), or shock, is a type of propagating disturbance that moves faster than the local speed of sound in the medium. Like an ordinary wave, a shock wave carries energy and can propagate through a medium but is characterized by an abrupt, nearly discontinuous, change in pressure, temperature, and density of the medium.For the purpose of comparison, in supersonic flows, additional increased expansion may be achieved through an expansion fan, also known as a Prandtl–Meyer expansion fan. The accompanying expansion wave may approach and eventually collide and recombine with the shock wave, creating a process of destructive interference. The sonic boom associated with the passage of a supersonic aircraft is a type of sound wave produced by constructive interference.
Unlike solitons (another kind of nonlinear wave), the energy and speed of a shock wave alone dissipates relatively quickly with distance.
When a shock wave passes through matter, energy is preserved but entropy increases. This change in the matter's properties manifests itself as a decrease in the energy which can be extracted as work, and as a drag force on supersonic objects; shock waves are strongly irreversible processes.

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  1. J

    Electical shock, electrocution questions

    HI, I couldn't decide which forum was the best to post these in. I have two questions regarding electricity and getting shocked, or electrocuted. 1. Being shocked from the spark plug leads on either small engines (lawnmowers) or cars. Classically, on either of these, you have a coil which...
  2. T

    When a star explodes, does the shock wave

    When a star explodes, does the shock wave move faster than the local speed of light? If it does, what effects would this have? A little explaining is in order... While the actual speed of light does not change (c in a vacuum) the overall progression of light is greatly slowed down due to...
  3. D

    Physics of a Vibration Dampener (Tennis shock absorber)

    Can someone explain to me the physics involved in this? Why does the dampener absorb some of the shock? Where does that shock go? This sort of stuff... Please do explain Thanks in Advance
  4. F

    Cheap Static Correction Measurement for Dog Shock Collars

    Is there a cheap way to measure static correction on a shock collar for dogs? Thanks in advance, Mac
  5. H

    Why isn't there shock wave in this case

    Hi everybody ! I have used FLUENT to do the following simulation ( it's 1.5 cm, not 1,5) http://upload.tinhco.net/thoai/debai.jpg I set 500 for "Number of Iterations". After running Fluent, I saw CL and Cd have convergenced, then I turn off the interation process. And here are my...
  6. L

    Frequency reponse of shock absorber piston in F1 car

    Hello everyone! This might be bit of the 'electrical engineering' topic - but maybe someone out there can help :) Does anybody have any idea of what the maximum frequency of a piston in a shock absorber of a forumula 1 car is? What do i mean: How many times does the piston (in a shock...
  7. wolram

    Electric Shock Causes Ticking Tooth - What Could it Be?

    I just had an electric shock, not a lethal one, it just burnt one finger a bit, but now i have a tooth that is going tick tick all the time, it is annoying and is hard to ignore. Any one have an idea why??
  8. I

    Why Doesn't a 1.5V Battery Shock You?

    Why is it that when you put your two finger on the opposite terminals of a 1.5 V battery, you don't get an electric shock? (Or maybe you do, but you just don't feel it?). I am guessing that this is because our body has a high resistance, is that correct?
  9. Cyrus

    Silicon Carbide Thermal Shock Parameter: 167C Explained

    I am looking for a material to use, namely Silicon Carbide, and it gives a "Thermal Shock Paramter - 167C" Obviously thermal shock is going to be failure when there is a rapid temperature change, but what does 167C mean? It's not a rate of cooling, just a temperature. I can't find anything on...
  10. P

    Calculating Shock imparted by an Impact

    I am designing a piece of test equipment that will be mounted onto a small rocket for meteorological testing. The people running the rocket side have mandated a series of tests that all test equipment must pass before being fitted. One set of tests are pretty severe shock tests...
  11. Astronuc

    News Future Shock - Decreased Grain Supply, Increased Cost

    I heard recently that Wheat (grain) production decreased due to drought in Australia and other areas, e.g. midwest US. Several countries have curtailed or reduced export and in some cases are now importing. At the same time, the cost of production has increased, in part due to increased energy...
  12. P

    Moving Shock Tables: Fundamentals of Compressible Flow Mechanics

    I have developed new tables for moving shock and I wonder if any one has seen these kind of tables? These tables appears in book "fundamentals of compressible flow mechanics". The book and software can be download from www.potto.org. If you seen these table please drop me a...
  13. R

    Can Holding a Spark Plug and Electric Current Shock Someone?

    Hi, is it possible to shock someone by forcing them to hold a spark plug in one hand and a piece of metal connected to an electric current in the other to cause like, let's say 3V of electricity to go through their body? Or is there something wrong with the setup?
  14. T

    Calculating Distance of Earthquake Epicenter Using P and S Waves

    Earthquakes produce several types of shock waves. The most well-known are the P-waves (P for primary or pressure) and the S-waves (S for secondary or shear). In the Earth's crust, the P-waves travel at around 6.5 km/s while the S-waves move at about 3.5 km/s. The actual speeds vary depending on...
  15. C

    Is there a difference between shock waves and compression waves?

    Ok, I watched a TV show where they showed a test of a building designed to handle an attack like the OKC incident. There was a visible overpressure wave on the high-speed film that hit the building and cracked the glass and knocked a couple pieces of sheetrock loose (the building otherwise...
  16. M

    Sonic booms and shock cones.

    Okay, I got this worksheet today and my teacher didn't explain to me what shock cones were. So here's the problems, and what I did so far to work them out. "An aircraft makes a supersonic pass 382 m over an observer. the shock wave pounds the observer after the plane is 405 m past her...
  17. M

    What Are Shock Cones and How Do They Relate to Mach Numbers?

    My teacher gave us a worksheet to prepare for the test tomorrow, and we never discussed anything about problems 10 to 14. I'm not asking for answers . . . just clarifications. 1.) What is a shock cone, anyway? 2.) What does Mach II, Mach III, etc. mean? 3.) Are there certain equations that...
  18. Ivan Seeking

    Snake in a Bottle: A Peasant's Shock

    While visiting her sister, Tsu saw our nephew who is currently in the Navy and who just returned from Singapore. He had an alcoholic beverage with a snake coiled up in the bottom of the bottle! For some strange reason, Tsu chose not to indulge. :biggrin: I did a little googling...
  19. zoobyshoe

    Preventing Static Electric Shocks: Tips and Techniques

    Every time I get out of my truck and touch the door to shut it, I get a zinger of a static electric shock. It's getting very annoying. I'm suspect I'm charging myself by rubbing against the seat cover as I get out. Anyone have any ideas how to stop this?
  20. L

    What Is the Shock Wave Cone Half-Angle at Mach 2.30?

    What is the shock wave cone half-angle for a supersonic airplane flying at Mach 2.30? Would you use Mach=1/sin(theta) and then divide by 2 to get the half angle? So 2.30=1/sin(theta)=12.9 degrees
  21. B

    Shock Wave Frequency: Observer, Emission & Calculation

    Is the frequency of the shock waves detected by the observer infinte? And, as I know, a shock wave can be produced even if the source didn't emit sound waves. When a object moving in a medium at a speed faster than the speed of medium's elastic wave's speed. In this case how we calculate the...
  22. magi

    MasterIs the existence of gravity shock waves in the universe possible?

    Gravity shock wave... Hi. What if there is gravity shock waves in the univers. I asked a professor once and he said that they can't exist becouse it need infinit energy to create a gravity shock wave. But what if they were created in the big bang so we have gravity shock waves now in the...
  23. R

    Bow Shock Waves: An Overview

    Does anybody has information about bow shock waves?
  24. BasketDaN

    Shock absorbers that only resist motion in one direction?

    I was just wondering if there are shock absorbers on the market that will allow motion in one direction freely, but resist motion in the opposite direction; thanks.
  25. J

    Help (Electrostatic/electric shock)

    here's a problem that I am currently working on. I know the theory, but I'm not quite sure how to start this particular problem: "Thomas was crawling around on the rug. When he reached for a metal truck, a prominent spark lasting 5mmsec appeared between his fingertip and the object. His...
  26. N

    Exploring the Role of Shock Waves in Star Formation from Interstellar Clouds

    I would like to ask that what character does shock wave (not pressure wave ) play in the forming of a star from the interstellar cloud?
  27. H

    Earthquake Impacts: 3 Microseconds & 1 Inch Off Axis

    I found this amusing: I just read the Wikipedia article on the recent quake/tsunami, which mentions that the earthquake may have sped up Earth's rotation, shortening days by 3 microseconds... but balanced that by noting that the moon slows days by 15 microseconds each year. It also mentions that...
  28. B

    The shock absorbing ability of steel

    can anyone explain the shock absorbing ability of steel? thank you
  29. B

    PDEs & Shock Waves: Understanding Inviscid Burgers' Equation

    Forgive me for the long post, but I'm in some desperate need of clarity on this matter. I just can't seem to grasp the whole shock wave concept, or at least the meaty part of it . I only have a couple of problems left to do to finish my HW I'm at an impasse until I dispel my confusion. I...
  30. wolram

    Shock Wave in Space: Vacuum or Medium?

    Im not sure if this is the right forum for this question as I am unsure where it fits. I always think of a Shock Wave as something that travels through a medium, as in a sonic boom from an aircraft, but some talk of shock waves in space, as in the shock wave from a supernova, is this the...
  31. Gokul43201

    Testing Your Shock Absorber Prototype: Min Drops to Determine Breaking Height

    You are designing a type of shock absorber that protects delicate objects from jolts during transportation. To test your prototypes, to decided to find the maximum height from which a crytal vase wrapped in your absorber can be safely dropped. You get a step ladder with 40 steps and decide to...
  32. Clausius2

    Shock Wave Relativity: Exploring Local Thermodynamic Properties

    Ok, imagine this experiment: I am in Mars, inside of a supersonic storm. There is a small sphere standing inside the incident flow, and I am in a laboratory viewing the shock wave caused by the sphere. I have some pressure measurements of the flow, (i.e around of the sphere surfice), so I can...
  33. U

    Does Home Grounding Protect from Electric Shock?

    If a very large amount of power was grounded say in house and all the taps for example were connected to the same circuit would somebody touching a tap get any sort of eletric shock. I have heard that some peoples TVs etc explode when their house gets hit by lightning even though they have...
  34. T

    Shock waves traveling around corners

    Can anyone in this section help me answer this question? Any help would be appreciated. Terry Giblin
  35. T

    Shock waves in crystals and frequency changes

    Shock waves propagating in photonic crystals can be used to lower or raise the frequency of light passing through them. It seems (to me) to be some kind of Doppler effect at work here. The electrons in the atoms of the crystal absorb the light, and as they move because of the propagating...
  36. 3

    Metallurgy, slip planes, shock theory

    I read in an old metal working book that when a auto body panel is struck sharply with a hammer that for a microsecond or nanosecond there is a vibration or "shock waves" that allows the grains of metal to slip past one another and re-arrange slight. I am desperately looking for an explanation...
  37. A

    News Shock & Awe Tactics: Exploring Baghdad "Liberation

    Shock and Awe tactics, huh? Gosh, they certainly love the slogans over there. What that means in non-sloganeering English is: we've flattened half of Baghdad to "liberate" them. See the book if you wish. http://www.dodccrp.org/shockIndex.html
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