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. C

    Shock to an infant when pulling power cord out of a wall socket

    My son occasionally pulls plugs from powerpoints. We tried to get a powerpoint cover but the strong tape here in Japan is weak and it fell off easily. I was just wondering how much electric shock he might get from pulling out the cord when the device (a fan) is operating. Its a two prong...
  2. T

    I Finite promise games, shock of my life

    I am shocked after reading this: http://googology.wikia.com/wiki/Finite_promise_games So, let's take strong Goodstein function. It is total, but this fact is unprovable in Peano Arithmetics. No problem, I just understand that PA is too weak. Goodstein function is total, just take stronger...
  3. T

    Calculating mass flow rate while assuming shock losses

    Below is a 2 part question regarding gravitational pipe flow, I have managed to do Q1) and have got an answer of 144 kg/s. However Q2 asks that shock losses be considered, Although I know how to calculate the shock pressure loss I am unsure of how to apply this to my calculation to get a new...
  4. A

    What is a very weak shock wave? (Gas Dynamics)

    I stumbled upon this concept when studying gas dynamics. What I get from my readings it must occur when Mach number is really close to 1. But I didn't understand how the property relations across a shock wave is affected by it.
  5. CK328

    Mathematical modeling of a mountain bike rear shock

    Evening all, I've recently undertaken a project where my roll is to analyse the suspension of a mountain bike. The suspension unit in question is a Rock Shox Monarch RT3. To give a brief summary: The shock uses compressed air as the spring, the pressure is adjustable via an air valve. The shock...
  6. JulienB

    Shock absorber (oscillation)

    Homework Statement Hi everyone! I'm still trying to make my way through the wonderful land of oscillations. That's going to take a while. :DD The springs and shock absorbers of a small truck have been conceived, so that the truck body sinks of a distance s = 100mm by full load (total mass m =...
  7. D

    I What happens if two moving shock waves collide?

    Say there were to be two normal shock waves that were moving towards each other at different speeds. What would happen when they collide with each other? Would the shock waves flow past each other or would they be reflected back from the direction they came from? Also how would you be able to...
  8. H

    Problem regarding a Normal Shock Wave and Blunt Nosed Object

    Am not sure if I've posted in the right section but I couldn't find anything relevant to Waves in Supersonic Flow, so apologise in advance! Post is a little long but I will appreciate any help! Academically am not very gifted and also have a mathematics disability so I tend to question even the...
  9. Greg Bernhardt

    Is it safe to be tased by a Taser?

    Today I was over at my wife's parent's house. My wife and her mom were doing a puzzle on a work bench. My wife told me she heard a buzzing under the work bench. Her mom has hearing problems and couldn't hear it but I certainly could, it was quite loud. I looked and it was coming from a lamp type...
  10. nicholas0211510

    Shock Wave Questions: Calculating Speed & Intensity

    How would one calculate the speed of a shock wave or intensity? For example, let's say something with a mass of 10 kg, with a velocity of 1000 m/s, travling in a straight line ,in Earth's atmosphere, at sea level . what formulas would one use to figure this out? Thanks in advanced
  11. adisabeba

    I get a shock when touching water pipe

    I am living in an apartment and suddenly we started to get an electric shock, at random, when touching a water tap. Since I am an Electrical Technician, I started my research on the origin of the problem, and after carrying out a series of tests I found out 'at the end' that turning off all...
  12. vikc

    Shock absorbent material to protect an egg

    I am doing the Bottle Rocket event for Science Olympiad and I have to have an egg strapped to an air pressured rocket which should not crack on the way down. What is the best and lightest material I can use to absorb the impact? I was thinking of a sponge or cotton. The rocket will be floating...
  13. N

    Electrostatic discharge current

    I understand that electrically charged objects such as a rubber balloon or even the human body can hold several thousands of volts. What's troubling me is that I know the current that results from an electrostatic discharge is not enough to cause serious damage or kill a human, yet if you touch...
  14. B

    Shock Waves Traveling to the Ground from a Jet

    A jet flying directly over you at an altitude of 3300 m produces a shock wave. The angle of the shock wave is 43 degrees. How long will it be until the sonic boom reaches you? How far does the jet travel during this time interval? I know that I can figure out the second part of this problem if...
  15. E

    Potential Difference and electric shock

    Electricity travels from higher potential to lower potential then why don't we get an electric shock while holding aa high potential wire without touching the Earth ( we are also at lower potential)
  16. A

    Totally Hypothetical, probably incorrect, Shock Wave Generation Mechanism

    So I was sitting around pondering about forces, and I found myself thinking about shock-waves. Whether they're caused by supersonic travel, or explosions, the pressure at the front of the wave-bow shock pressure is a force. So I started thinking of a way to generate them without having to go...
  17. kelvin490

    How can shock waves travel faster than sound?

    Shock wave is caused by the disturbance of air by the airplane. When it propagate the mechanism should be the same as that of longitudinal sound wave. Why sometimes it can travel faster than sound? (also see: http://physics.info/shock/ )
  18. H

    Height adjustable Shock absorber possible?

    Greetings, in my total distraction of designing the ultimate Off-road/Overland vehicle, I've been thinking about the following matter: Is it possible that a vehicle can be raised/lowered by pumping/removing extra oil into the shock absorber? And if so, would it affect the ride? Could it be...
  19. A

    Shock absorption properties better from casting or forging?

    Hi I want to ask which of the cast steels or forged steels provide with better shock absorption? The component has to be used in the under chassis of heavy trucks in bumpy roads. Can anyone help me with that? Thank You
  20. J

    Is the Voltage the Only Factor in Electrical Shocks from Automotive Batteries?

    It is said that with dry hands, you can touch the poles of a car battery and it will not shock you. I understand this is because dry hands have a very high resistance. Now if you have wet hands, or even worse if you have needles stuck into your skin that are attached to the battery posts, this...
  21. S

    Understanding Compressible Shock Waves: Exploring Theta, Beta, and Mach Curves

    Hi all, I have some prob to undestand the shock wave in compressible flow, more precisely the "theta, beta, Mach curve) - Why when "theta" exceeds theta (max) there is no oblique shock? (how we can explain this physicaly)? - What is the difference betwwen weak shock and strong shock? - why in...
  22. R

    Static electricity shock: Can it ever be lethal?

    I was wondering, is it possible to charge oneself with static to an extent that would be lethal or even damaging to a significant extent beyond the usual discomfort? What are the governing calculations? Instead of the usual carpets would any other materials in an exceedingly dry climate give...
  23. H

    Calc Oblique Shock Angle for Supersonic Flow 0-5 Degrees

    Is there an equation to calculate the oblique shock angle for supersonic flow when the given angle of attack is greater than 0, but less than the half angle? In my particular practical experiment, the half angle of the aerofoil is 5 degrees, so want to get a variety of figures between 5 and -5...
  24. G

    Do birds on transmission lines experience electric shock?

    Gruxg has posted a thread on November 4, 2012, titled as "If you touch a live wire without touching the ground, do you get an electric shock?". I think that this thread would deserve more consideration as it discusses an essential subject but unfortunately it is closed for further replies, so I...
  25. J

    Working of capacitor in shock pen

    Can anyone explain the use of capacitor in a shock pen
  26. enorbet

    Exploring the Formation of Shock Diamonds

    Greetings Recently I read that radio jets from Quasars and Radio Galacies exhibit a behavior similar to shock diamonds which reopened a creaky old door in my mind because i first started reading about Shock Diamonds as a child of about 8 which may be part of my difficulties in understanding this...
  27. S

    Shock in Water and Water Pipes

    Hello everyone... Help me out.. I installed a geyser 3 weeks back which has a rating of 15A and I connected it to a 32A MCB. This is connected to a 16A separate MCB in the main board. Whenever I turn on the geyser, it works for some 10mins and then turns off without water getting heated. I...
  28. B

    Electric Charge in Dogs - Science Explained

    Hi, I've got a question which I can't google, I' haven't found anything about this. My dog simply shock me. Yes, I know static electricity and stuff but I wonder why this happens only when he is excited about something? For example I tell him that we're going for a walk and when I touch him he...
  29. P

    What happens when 2 shock waves collide?

    If I have 2 shock waves propagating at different speeds in a tube, let's say to the right. Let's say initially one of the shocks (shock 1) is ahead of the other (shock 2), but shock 2 is faster than shock 1, so eventually shock 2 will catch up to #1. What happens when they catch up? Do they...
  30. R

    Does experiencing a static shock mean that you are grounded?

    If I built up static in me and then touch a doorknob and get shocked, am I then sufficiently grounded to be able to touch electrical components? Or was it just that the extra electrons were discharged and I should still ground myself in another way before touching electrical components?
  31. J

    What are shock interaction regimes?

    I have been asked to determine the "shock regime" of a oblique shock / bow shock interaction based on the angle of the impinging shock and flow conditions. What does this mean? My initial thoughts were that I was being asked to determine whether the shock was strong or weak, but since the...
  32. M

    Is This the Correct Method for Solving a Condensation Shock Problem?

    Homework Statement Total temperature of mixture= 600 K, mass fraction of vapour to mass of total mixture=0.01 Homework Equations Ideal gas law, Mach area relations, Rankine-hugoniot equations The Attempt at a Solution Applied Clausis-Clapeyron relation to find vapour pressure, Then found...
  33. T

    How do bombs create shock waves and blast waves?

    How does bombs produce shock wave and blast waves. ...
  34. A

    Euler Equations, Sod shock tube & conservation

    Is momentum conserved? I am considering the Euler equations in conservative form and solving the Sod shock tube problem I have written a Godunov finite volume type solver. It solves for density ρ, momentum ρu, and total energy E; therefore, I would expect all of these quantities to be...
  35. L

    Grounding SMPS Power Supply: R, C, & Shock Risk

    Assuming a 2 pin connector for an SMPS power supply, what is the role of the R and C that are connected to Case ground. Usually R is in Megaohms and C around 0.1uF,2KV. IS there a risk of shock when the case is touched?
  36. A

    How can the deflection of a rod be lengthened to stabilize the shock at T = 2.51?

    The current of a regenerative shock absorber is modeled by I = -5e^(-0.5t) cos t - 10e^(-0.5t) sin t Given that the charge, q, in an electrical current is related to, I by I = dq/dt and that at t = 0 the charge of the regenerative shock absorber is q=80, find the charge when t = 5 Hint=...
  37. J

    Which is the problem with electric shock?

    Which is the problem when a human being is electrocuted: the high voltage and/or the high current? What the high voltage make in the body human (such as brain, heart and other organs)? What the high current make in the body human (such as brain, heart and other organs)?
  38. Y

    Pretension of spring based on sideway shock

    Hi all, First to clarify: this is no homework question. I am working on a construction and am really puzzled about the following problem. I need a spring to hold an object in place during sideway shocks. I am really puzzled about the fact if friction helps one or two times. In other...
  39. gfd43tg

    Normal Shock Table: P02/P01 & P1/P02 Meaning

    Hello, I am wondering, on a Normal Shock Table, what are the two most right columns supposed to mean? What is the ratio P02/P01 and P1/P02 supposed to be?
  40. N

    Calculating Shock Absorber Energy Dissipation for Car Bounce

    Homework Statement How much energy must the shock absorbers of a 1240 kg car dissipate in order to damp a bounce that initially has a velocity of 0.840 m/s at the equilibrium position? Assume the car returns to its original vertical position. Homework Equations Fs = -kx The spring...
  41. Eagle9

    What the destructive force of the shock wave depends on?

    When the powerful (nuclear) bomb explodes it generates the shock wave that destroys everything around it. I want to know, does the force of this shock wave depend on the air pressure and density? Imagine that we have got powerful (nuclear) bomb and the object (rocket in this case) that is...
  42. D

    Energy and radius of a shock wave

    Homework Statement A shock wave moves away from the center of the explosion, its pressure is decreasing, and its speed tends to a constant value. In the filming of a particular explosion, the following data was obtained: t(s): 0, 0.02, 0.04, 0.06 ,0.08, 0.1, 0.12, 0.14, 0.16, 0.18...
  43. V

    Supersonic motion: no backward propagating shock waves

    There was a recent thread (now closed) where I claimed that a body accelerating beyond the speed of sound emits a shock wave that propagates spherically backward in the rear hemisphere. I have reviewed literature on fluid dynamics and it is quite clear to me now that I was wrong. There is no...
  44. T

    What exact speed point does shock wave start to appear

    what exactly speed point does shock wave will start to appears..
  45. M

    Velocity of a particle exposed to a shock wave?

    I need to understand how much kinetic energy a particle can absorb which initially is at rest and suddently is exposed to a shock wave. Detonation velocities are very high, on the order of 6000 m/s, but I assume this is the velocity of the shock front and not of the gas molecules themself...
  46. chasrob

    How Can a Superpowered Character Control Their Abilities to Avoid Catastrophe?

    Yep, half light speed or thereabouts; superhero story :). I'm writing a story about this fellow who gets super powers, including super speed. He can move, fly, at up to 100 000 miles per second. He can also move around at normal speed if he concentrates on what he's doing. Right after he...
  47. J

    What Material absorbs shock better? Rubber or plastic?

    For example a phone in a case is dropped, would it suffer more in a plastic case or a rubber case? Thanks
  48. R

    Opening/closing valves and shock types caused

    Hi, I`ve had past experiences with pressure switches giving "strange" (pulsed) signals due to nearby discharge valves closing or opening. Looking a little into it I run into reading about compressibility theory and "shock tubes". Just for info, a "shock tube" is a tube with 2 zones...
  49. V

    Automotive Use of nitrogen gas in modern shock absorbers

    nitrogen gas is said to prevent cavitation in shock absorbers and thus provide a comfortable ride.. i want to know what actually happens in a shock absorber when nitogen gas is used. how does it prevent cavitation?
  50. E

    Exploring the Mpemba Effect: Kinetic Energy and Temperature Shock

    Hi my name is Bruno, I'm 19, I'm currently finishing my 12nd grade on arts. I'm annoyed because no one I know can properly discuss the Mpemba effect with me. So, I'll go as fast as I can on this. The scenario. We have a cup of water let's say for example at 80 degrees Celsius ...
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