What is Compression: Definition and 632 Discussions

Lossless compression is a class of data compression algorithms that allows the original data to be perfectly reconstructed from the compressed data. By contrast, lossy compression permits reconstruction only of an approximation of the original data, though usually with greatly improved compression rates (and therefore reduced media sizes).
By operation of the pigeonhole principle, no lossless compression algorithm can efficiently compress all possible data. For this reason, many different algorithms exist that are designed either with a specific type of input data in mind or with specific assumptions about what kinds of redundancy the uncompressed data are likely to contain.
Lossless data compression is used in many applications. For example, it is used in the ZIP file format and in the GNU tool gzip. It is also often used as a component within lossy data compression technologies (e.g. lossless mid/side joint stereo preprocessing by MP3 encoders and other lossy audio encoders).
Lossless compression is used in cases where it is important that the original and the decompressed data be identical, or where deviations from the original data would be unfavourable. Typical examples are executable programs, text documents, and source code. Some image file formats, like PNG or GIF, use only lossless compression, while others like TIFF and MNG may use either lossless or lossy methods. Lossless audio formats are most often used for archiving or production purposes, while smaller lossy audio files are typically used on portable players and in other cases where storage space is limited or exact replication of the audio is unnecessary.

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  1. L

    Calculating Vibration Frequency of 1100 kg Car with 68 kg Driver

    The springs of a 1100 kg car compress 6.0 mm when its 68 kg driver gets into the driver's seat. If the car goes over a bump, what will be the frequency of vibrations? I tried to use the weight of the man (68 kg) and the compression distance (6 mm) to find the spring constant. I then tried to...
  2. P

    Analyzing Block & Spring Compression: F = -kx & W = -0.5kx^2

    A block of mass 0.528 kg slides with uniform velocity of 3.85 m/s on a horizontal frictionless surface. At some point, it strikes a horizontal spring in equilibrium. If the spring constant is k=26.7 N/m, by how much will the spring be compressed by the time the block comes to rest? What is the...
  3. R

    Energy Conservation Spring Compression Problem

    This is Problem 10.46 from the Engineering Physics Book by Knight. A vertical spring with k = 490 N/m is standing on the ground. You are holding a 5.0 kg block just above the spring, not quite touching it. a.) How far does the spring compress if you let go of the block suddenly? b.)...
  4. S

    Maximum compression of a spring

    Homework Statement A 50-kg mass is dropped from a 20-m height onto a very long, initially uncompressed spring of force constant k = 100 N/m Homework Equations Ueo=Ugf+Uef F=k(Lenght Final-length initial) The Attempt at a Solution I tried using Ueo=Ugf+Uef, and i couldn't...
  5. T

    Thermodynamics compression problem

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  6. S

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  7. M

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    Homework Statement A package of mass 8 kg sits at the equator of an airless asteroid of mass 5.8 105 kg and radius 32 m, which is spinning so that a point on the equator is moving with speed 4 m/s. We want to launch the package in such a way that it will never come back, and when it is very...
  8. R

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  9. M

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  10. S

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  11. S

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  12. M

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  13. A

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  14. A

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  15. L

    Exploring Engine Braking and Compression Effects

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  16. A

    Calculate Energy of Compression for Hydrogen

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  17. P

    Max Speed & Spring Compression of 10kg Object on Frictionless Incline

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  18. Q

    Ultra-lossless compression algorithm

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  19. G

    Adiabatic Compression: Understanding Internal Energy and Work in Gases

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  20. R

    Max Compression of Frictionless Blocks & Spring

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  21. D

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  22. A

    Free body diagram : Compression and Tension

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  23. H

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  24. R

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  25. D

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  26. F

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  27. 2

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  28. D

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  29. B

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  30. R

    How Do You Calculate Work Done in Lattice Compression?

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  31. D

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  32. S

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  33. S

    Solving Compression Problem: Water Skier & Tow Rope

    A 57-kg water skier is being pulled by a nylon (Young's modulus 3.7 x 109 N/m2) tow rope that is attached to a boat. The unstretched length of the rope is 18 m and its cross-section area is 1.9 x 10-5 m2. As the skier moves, a resistive force (due to the water) of magnitude 190 N acts on her...
  34. M

    Calculating Compression of a Concrete Stand Under a Heavy Statue

    A 2480-kg statue is placed on top of a cylidrical concrete (Y = 1.6 x 10^10 N/m2) stand. The stand has a cross-sectional area of 6.5 x 10^-2 m2 and a height of 2.2 m. By how much does the statue compress the stand? this one deals with volume deformation but I'm unsure of how to start it out...
  35. S

    Another Diffcult Bone Compression problem.

    A gymnast does a one-arm handstand. The humerus, which is the upper arm bone between the elbow and the shoulder joint, may be approximated as a 0.26-m-long cylinder with an outer radius of 1.12 x 10-2 m and a hollow inner core with a radius of 3.7 x 10-3 m. Excluding the arm, the mass of the...
  36. R

    Particle dropped on platform with spring - Compression of springs

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  37. R

    Spring compression distance from a block sliding down a ramp

    A 10kg box slides 4.0m down a frictionless ramp, then collides with a spring whose spring constant is 250 N/m. (Also, the ramp is angled at 30 degrees). a). What is the maximum compression of the spring? b). At what compression of the spring does the box have its maximum velocity? I started...
  38. Repetit

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    Hey! "Calculate the work done on 1 mole of a perfect gas in an adiabatic quasistatic compression from volume V1 to V2." The work done on the gas in this compression is: -\int_{V1}^{V2} P dV Because we are talking about an ideal gas the ideal gas law applies so...
  39. K

    Solve Compression Distance for Mass Spring Train Collision

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  40. C

    Question about spring compression

    A 12 kg block slides from rest down frictionless 35 degree incline and is stopped by spring w/ constant of 3.00x10^4 N/m. The block slides 3 m from the point of release to the point of rest against spring, how far has spring compressed? Now I know this involves the equation Ws= 1/2kxmax2, but...
  41. I

    Calculating Water Flow Rate Under Compression

    I would like to know how to calculate the flow rate of water under compression by a hydraulic weight. How do you calculate using the value of the weight on top of the water and the height of the water in a straight column?
  42. D

    Solving an Inelastic Collision with a Spring: Maximum Compression

    here is how it goes, A block of mass m_1 = 2.0kg slides along a frictionless table with a speed of 10m/s. Directly in front of it, and moving in the same direction, is a block of mass m_2 = 5.0kg moving at 3.0m/s. A massless spring with a spring constant k=1120N/m is attached to the backside of...
  43. S

    Spring designed for compression

    Let's say, we have a spring designed for compression which is kept vertically on a table. Now if we press on the spring from the top, it will naturally compress. My question is, what will happen if we compress the spring from the middle instead of from the top. Will the portion above the...
  44. C

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    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...
  45. S

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    https://chip.physics.purdue.edu/protected/Halliday6Mimg/h10p33.jpg A block of mass m1 = 2.5 kg slides along a frictionless table with a speed of 12 m/s. Directly in front of it, and moving in the same direction, is a block of mass m2 = 6.2 kg moving at 3.7 m/s. A massless spring with spring...
  46. D

    Is Vertical Compression Correctly Applied in This Function Transformation?

    Q. Given f(x)=2(x^2)-4 , determine the new equation g(x) after a vertical compression by a factor of 1/2. The answer provided by the book is g(X) = (x^2)-2, but shouldn't it be g(x) = (x^2)-4 ? Help will be much appreciated. Regards, Adam
  47. R

    Energy Conservation - Rock compression

    A 7.94 kg stone is resting on a spring. The spring is compressed 10.2 cm by the stone. (a) Calculate the force constant of the spring. (b) The stone is pushed down an additional 28.6 cm and released. How much potential energy is stored in the spring just before the stone is released? (c)...
  48. D

    How Far Will the Spring Compress When Dropping a 5.8 kg Block?

    A vertical spring with k = 495 N/m is standing on the ground. You are holding a 5.8 kg block just above the spring, not quite touching it. How far does the spring compress if you let go of the block suddenly? i thought i could just use k = F/distance so 495(D) = (5.8)(9.8) D = .1148...
  49. S

    Solving a Spring Compression Puzzle: Work Done by Gravity

    Spring Question! A 250g block is dropped onto a relaxed vertical spring that has a spring constant of 2.5N/cm. The block becomes attached to the spring compresses the spring 12 cm before momentarily stoppoing. While the spring is being compressed, what work is done on the block by (a)The...
  50. R

    Compression / Momentum in a cylinder

    Ok...this is a thought model to help me understand some things you have a cylinder with a gas in it. You also have moveable piston. I move the piston into the cylinder, compressing the gas by 25% of the original volume. I know the pressure of the gas will increase for two reasons...
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