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.

View More On Wikipedia.org
Recent contents Top users
  1. N

    [Fluid dynamics] Normal shock wave problem

    Homework Statement Air, supplied by a reservoir at 450 kPa, flows through a converging-diverging nozzle whose throat area is 12 cm^2. A normal shock stands where A1 = 20 cm^2. (a) Compute the pressure, p2, just downstream of this shock. Still farther downstream, where A3 = 30 cm^2, estimate (b)...
  2. K

    The idea behind a reverse shock

    So in a supernova explosion for example (5th slide) http://www.astro.princeton.edu/~burrows/classes/541/blastwavesChisari.pdf Ambient medium is accelerated, compressed and heated. It pushes back into the ejecta, creating a reverse shock. Why does it do this and not just emit a drag...
  3. T

    Van de Graaff Generator - Shock vs. No Shock?

    Hello all, I have a quick, albeit probably ignorant (forgive me) question generated by (bu dum) observations of a van de graaff generator. In particular, two distinct scenarios caused me to question what was going on. Scenario 1 – I’m standing on a plastic stool, with one hand on the...
  4. M

    Bicycle seat post shock absorbtion.

    Hi i am currently studying a bicycle seat post suspension unit. It is one of the lower end of the range models which consists of a spring and a rubber dampener. Basic outline in cad below. http://imageshack.us/a/img407/1720/drawing1layout1.th.jpg I would like to know the calculations behind...
  5. L

    Method of characteristics and shock waves

    Hi all! I just wanted to ask if anyone is finding the usage of method of characteristics difficult ? I sort of feel, that it is a very simple approach to solving PDE's, but I get easily lost, when for instance, we have to keep switching back and forth between variables and such. When it comes...
  6. R

    Electric shock via ground that becomes live.

    Was reading a crane-operations manual and it had a Section on what to do if your boom accidentally contacted overhead electrical wires. It advised not trying to step out of the cab (of course); but in case of imminent danger advised jumping out (makes sense). The interesting part came after...
  7. J

    Can sound waves travel in a material at a speed faster than the speed of sound?

    I'm just trying to get a better grasp on sound waves and shock waves. Let's say I have a cylindrical rod of length L with no forces acting on it, and I push on the back of it with some constant velocity less than the speed of sound, c, of the material the rod is made of. Will the front of the...
  8. A

    How and why are shock waves produced in breaking objects?

    The example I have in mind is when a pole vaulter's pole breaks. I remember at last year's Olympics one of the commentators made a commenf about thw shock waves thag would've been traveling through the pole and the guy's hands when it broke. I did a search and it was mentioned in some...
  9. E

    Gas Dynamics (Compressible Flow) Normal Shock Wave

    Homework Statement Suppose that a blast wave, which might have been initiated by an atomic bomb explosion, is traveling through air at standard atmospheric conditions with a speed of 60,000 m/s find change in ( pressure , temperature , stagnation pressure , velocity ) produced by the wave...
  10. M

    What is the duration of impact for a steel ball hitting a plastic box?

    Hello, I'm trying to estimate how long the impact of a steel ball hitting a plastic box would be. The actual case: you drop a steal ball d=0.51mm, m=0.54kg from h=0.74m onto a box made of plastic, the impact speed is 3.86m/s and force 4J. I want to know the deceleration speed during impact...
  11. S

    Can Decreases in Pressure Propagate as Shockwaves in Fluids and Gases?

    In low pressure gases, speed of sound is independent on pressure and depends only on temperature. Therefore increase of pressure will propagate as shockwave - front of the wave compresses and heats the gas, allowing the rear of the wave to travel faster and pile up into a shock. By the...
  12. P

    Why is electric shock more dangerous with wet hands in welding operations?

    in welding operation , you never hit by electric shock,why?
  13. A

    Difference between blast, shock, pressure and sound waves?

    What are the differences (I'm really trying to understand the differences in the context of an explosion). When you hear it, are you hearing all 4 waves? Which waves cause the damage and why - why not the others? Also, when NASA launches the space shuttle, they release water to absorb the...
  14. Y

    Air Hose & Valve - Maximum Nominal vs Shock Pressure

    Hey guys I'm designing an air cannon robot and I need your help determining what valves and hoses i need to get in terms of maximum pressure. Based on my research, the maximum pressure ratings for hoses and solenoid valves are for constant pressure and even flows, but because I'll be making an...
  15. L

    How does a shock absorber work or should work?

    An hydraulic shock absorber of a vehicle operates, usually, by viscous friction: the braking force is proportional to the relative speed of the mechanical parts (piston sliding in cylinder) through passage of the fluid (oil); in some more sophisticated cases there are valves that reduces the...
  16. D

    MHB Analysis of Shock Formation from Traffic Light Red Signal

    Suppose traffic is moving uniformly with a constant density $\rho_0$ when a traffic light turns red. At time $t = 0^+$, the initial density profile is then modeled according to the figure below. The resulting wave motion of the disturbance is governed by $$ \frac{\partial\rho}{\partial t} +...
  17. E

    Calculate approximately G-force applied on Car shock absorber

    I have to do some dataacquisition from a car with some accelerometers. 4 accelerometers is placed on the wheels before the shock absorber. And i need to calculate the maximum applied G-force on the accelerometers. Just an approximately value, not taking in account the type of wheel...
  18. T

    Solving for shock wave angle using Mach and deflection angle

    I am trying to show how the shock wave angle varies as I hold the deflection angle constant and increase the Mach number. I am trying to solve for Beta (shock wave angle) using the theta-beta-mach relation: tan(θ)= 2cot(β) * (M2sin2(β)-1) / (M2(1.4+cos(2β))+2) This seems like it should be...
  19. A

    What Would Happen If a High Mass Object Hit a Wall at High Velocity Near Me?

    If an object of VERY high mass were to hit a hypothetical wall at a high velocity and the wall somehow withstood that, what would happen to you if you were standing on the other side close to the wall but not touching it? Would there be some sort of wave transmitted through it? If so, would this...
  20. S

    Shock load due to high pressure gas flowing into container

    Hello, I am new here so I apologize in advance if my question is not formatted as it should. I have an application where a large pressurized vessel is releasing part of its contents (gaseous) into an "empty" container (air), much smaller, that is at atmospheric pressure. I need to know if the...
  21. V

    I get shock when I touch Grounding (earthing) wire

    Hello experts. This is a unusual behaviour. I moved to new house, an apartment newly constructed less than a year old. I first noticed shock when I was disammbling my computer , i immediately took out multimeter and tester. First checked with tester, it did not show any symptoms of...
  22. chemisttree

    Heliosphere's Long-theorized Bow Shock Does Not Exist

    "New results from NASA's Interstellar Boundary Explorer (IBEX) reveal that the bow shock, widely accepted by researchers to precede the heliosphere as it plows through tenuous gas and dust from the galaxy, does not exist." - Maria Martinez, SwRI Roadrunner, June 2012 So Voyager must actually...
  23. U

    Formation of shock waves and gas dynamics of flow in a nozzle.

    Hi I have a few questions regarding gas dynamics... 1. when M=1, dA=0...what does this mean? Does it imply that if we have a converging (subsonic) nozzle with its exit mach no,say 0.8, and then direct the flow to a constant area tube, then we have to attain M=1? 2. When we know the length...
  24. C

    Why does my laptop freeze when I shake it while watching a movie?

    My laptop is equipped with hard drive shock protection. If I am watching a movie and the accelerometer senses a perturbation (me shaking the computer) the image is immediately frozen, but there is no interruption in the sound. Why is this the case?
  25. S

    Exploring Shock Waves: Supersonic Flow Experiments

    Homework Statement Anyone know of any experiments I can do show demonstrate a shock wave or supersonics flow ? The Attempt at a Solution Closest thing I can think of is whipping a whip, because the end moves supersonic
  26. F

    The shock required to detonate C4

    Hi, I need to know how much shock is needed to detonate a C4 plastic explosive for my report in chemistry. I searched for it, but I didnt find a certain number. Somewhere I read it's about 4900 m/s of detonation velocity needed to create the shock, but it was from a source I wouldn't trust...
  27. P

    I get shock when i touch my electronic equipments

    Hi all, i get shock when i touch any of my electronic equipments (washing machine etc). To avoid shock i need to remove the connection from the socket and then only i can do maintenance and put the connection back to the socket and operate. Obviously i think earthing is the problem before i...
  28. A

    Equation of temperature increase by shock wave

    【HELP】Equation of temperature increase by shock wave Hi there! What is the equation of the temperature increase when the ideal gas swept by a planar shock wave (Mach number, M)? Thank you!
  29. J

    Difference between blast & shock wave

    Hi guys and gals, with respect to SNRs (or anything for that matter) What is the difference between a shock wave and a blast wave? Is it just that a blast wave is a sharp peak in the change in variables, where as a shock wave has a region behind it in which the variables gradually...
  30. T

    Spring Constant of a Spring in a Shock Absorber?

    Homework Statement What is the spring constant of a spring in a shock absorber? Also, does a spring constant of 288 N/m sound right for a regular spring such as the one attached?
  31. N

    Why Can We Experience An Electric Shock From Neutral

    I have always been under the impression that the "Live" conductor was the most dangerous conductor. The Live carries 120V (US) 240V (UK) and the Neutral carries 0V, but yet it is still possible to get an electric shock from a Neutral :confused: Why is this possible? Is it because it is...
  32. S

    Difference between shock wave and shock ?

    So I know what a shock wave is but what's a shock ? is it just the front of the shock wave ?
  33. A

    Questions about shock waves from explosions and impacts

    1) How does an explosion or impact (e.g. meteorite) create a pressure wave? In the case of a meteor, if kinetic energy is being transferred into the wave, how does this conversion take place? 2) Is it the shock wave from an explosion or impact (e.g. meteorite) just the collision of air...
  34. G

    Design Bicycle Cargo Rack w/ Shock Absorbers for Laptop

    I am trying to design a bicycle cargo rack that uses shock absorbers to protect sensitive equipment (i.e. a laptop computer). I have data for the maximum height from which laptops can fall without damage as well as the maximum acceleration to which they may safely be subjected. I am planning to...
  35. N

    Can Solenoids Be Used as Shock Absorbers Through Electromagnetic Damping?

    Is it possible to use a solenoid as a shock absorber? i.e run current through the solenoid, producing a magnetic field opposing a separate magnet attached to whatever it is receiving the shock impulse, thus dampening the effect according to the amount of current input.
  36. U

    How fast do you have to heat air to create a shock wave?

    Suppose you have a 1cm diameter heat source suspended 2m above the ground. How many watts of heat energy does it need to expend to create a shock wave?
  37. B

    Artillery Recoil Mechanism as Dual-Action Shock Absorber

    I've just viewed the National Geographic Channel's "Engineering Connections" program. specifically, the episode entitled "Airbus380", and that episode's discussion of the A380's landing gear shock absorbers, which used bicycle pumps filled with water to illustrate the basic principle of...
  38. P

    Eco-material selection. Shock absorber.

    As part of an assignment I have to redisign a product using an eco-material. I choose phone covers. From the silicone, rubber or plastic ones I intend to redisign using bamboo or cork. I would like to have some insight on the matter, what are the main properties i should be looking for...
  39. S

    Why do we get SHOCK if we touch current?

    why do we get SHOCK if we touch current?? when current pass through our body we get feeling of shock., why it happen?? person may turn black or die if exposed to high volt shock for long time?? why it hapens?:rolleyes:
  40. R

    Random Shock From Water Heater / Geyser

    Dear Friends and Senior Members , I am from India, Asia and we have the 240 V electrical system. We also have Geyser / Water Heater installed in our home 2 Nos. From the past 2 months I observe that sometimes, really sometimes the water heater installed in my room gives shock, I mean the...
  41. B

    Shock when touching an electric fence

    Hello Everyone, If you are grounded and touch an electric fence that is at 10,000V, say, you will experience a shock. What happens if you were to jump in the air when touching the fence? Would you still feel a shock? I'm getting confused because even in the air, your body is still at the...
  42. A

    Why do we get electric shocks when there is no potential difference?

    so i have learned that potential difference always occurs between points which have some common node that is if you have two circuits which don't have anything in common there will not exist any potential difference between any two points my question is why do we get electric shock when we touch...
  43. F

    What is the Mass of a Box in a Car's Trunk Based on Rear Shock Compression?

    Homework Statement When a box of unknown mass is placed into a trunk of a car, both rear shocks are compressed a distance of 7.00cm. If we assume the two rear shocks are made from springs, each with a spring constant of 35,000.00N/m, what is the mass of the box? (Assume g = 9.80m/s2)...
  44. A

    If a bullet was singing a song, what would the shock wave sound like?

    I'm trying to wrap my head around shock waves produced by bullets and their properties. In particular I'm interested in what affects the duration of the shock wave in time. Say someone shoots at me, the bullet passes near me, and I hear the shock wave produced by the bullet. If you look...
  45. R

    Is it the Resistance or Capacitance of Earth that Causes Electric Shock?

    Say you touch the hot wire and a piece of plumbing simultaneously. Then current flows through the hot wire, through you, to the ground, and I assume (though I'm not sure) to where the ground wire is tied to the neutral wire (at the breaker panel). But is the current in the ground mainly through...
  46. W

    Which shock is dangerous: 1.High V &Low I. 2.Low V & high I.

    Which shock will be most dangerous for human 1.High Voltage and low current or 2.High current and low voltage
  47. S

    Understanding Shock Waves and Entropy in Fluid Dynamics"

    Hello, I was wondering what was the effect of a normal shock wave on the physical properties of a fluid. How does the entropy (and perhaps pressure, temperature and density) vary from upstream to downstream of a normal shock wave? Thanks for your help.
  48. G

    Choosing the Right Material for Shock Absorption: A Guide

    Hello! I’ve recently become very interested in Sorbothane as a shock absorbing material, with the purpose of protecting sensitive equipment of mine from drops. My background on physics is limited and I would really appreciate any help, especially since Sorbothane can be costly and I’m a...
  49. Y

    Tesla Coil Shocks: Health Effects & Risk

    A friend of mine grabbed a handheld 10,000 volt tesla coil (the metal end) in one hand and a florescent bulb-tube thing in the other, and showed me that he could light the florescent tube using the electricity from the tesla coil. My question is, why did it not shock him, and are there any...
  50. V

    Shock Absorber Design Through Matlab Iteration

    Calculating area under graph from results of a for loop Im currently designing a shock absorber for an aircraft undercarriage, i have input all the relevant information and formulas into Matlab and created an M file with a functioning for loop giving a graph. The problem I'm having now is that...
Back
Top