What is Piston: Definition and 392 Discussions

A piston is a component of reciprocating engines, reciprocating pumps, gas compressors, hydraulic cylinders and pneumatic cylinders, among other similar mechanisms. It is the moving component that is contained by a cylinder and is made gas-tight by piston rings. In an engine, its purpose is to transfer force from expanding gas in the cylinder to the crankshaft via a piston rod and/or connecting rod. In a pump, the function is reversed and force is transferred from the crankshaft to the piston for the purpose of compressing or ejecting the fluid in the cylinder. In some engines, the piston also acts as a valve by covering and uncovering ports in the cylinder.

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  1. M

    Why does the area of a piston have no effect on its settling height?

    Dear all I am a secondary and sixth form teacher in London and I have come across a puzzling situation involving a piston. Imagine you can set up a piston of known mass resting on a gas beneath. The piston will come to rest at a certain height from the bottom of the tube. We can work...
  2. M

    Why Does the Torque Curve Drop Off at Low RPM in a Typical Piston Engine?

    I’ve been searching for an answer to this question on the web for 3 hours. Thought I would find it quickly, but, noooooo. I’m trying to understand why crankshaft torque falls off at low RPM in normally aspirated piston engines. I think I understand the high end of the torque curve OK. At...
  3. B

    How Does the Spring Constant Affect Piston Equilibrium?

    Homework Statement The closed cylinder in the figure has a tight-fitting but frictionless piston of mass M. The piston is in equilibrium when the left chamber has pressure p0 and length L0 while the spring on the right is compressed by delta L. The spring constant of the spring is k...
  4. Z

    Piston volume and pressure problem

    This seems like it should be really basic, so it's annoying me that I can't figure it out. Homework Statement One cylinder in the diesel engine of a truck has an initial volume of 600 cm^3. Air is admitted to the cylinder at 30 degrees celsius and a pressure of 1.0 atm. The piston rod...
  5. V

    Derving piston position and instant velocity

    hey guys, Im doing a question where it asks to derive the instantaneous velocity of the piston. We are given the potion of the piston as a function of instantaneous angular displacement of the crank. Now I checked the answer...and i m not sure how the \omega gets into the answer. if I take the...
  6. F

    Ideal Gas in Cylinder with Piston (Conceptual)

    You have a cylinder with an ideal gas inside, enclosed by a piston. There is a valve on the side of the cylinder could let gas through if opened. The valve is then opened and some of the gas escapes slowly while maintaining thermal equilibrium. Once it is closed, the piston is a little lower...
  7. M

    Volume of gas in a cylindrical vessel on which a piston has been placed

    [SOLVED] volume of gas in a cylindrical vessel on which a piston has been placed Homework Statement A cylindrical vessel with a tight but movable piston is placed in a vertical position so that the piston, whose area is 60 cm2, is subject to atmospheric pressure. When the gas in the vessel...
  8. L

    Piston Question that I do not understand

    [SOLVED] Piston Question that I do not understand Homework Statement A block rides on a piston that is moving vertically with simple harmonic motion. (a) If the SHM has a period 1.0s, at what amplitude of motion will the block and piston separate? (b) If the piston has an amplitude of...
  9. S

    Work done in Compressing a fluid in a piston (Bulk Modulus)‏

    Homework Statement I am trying to solve one theoretical problem. If I had an Iron piston cylinder with radius of 1 cm, such that it contains 1 liter of water(therefore about 318 cm tall), ( say Bulk Modulus of water is 1 GPascal), How much work(in joules) will be required to depress...
  10. J

    Hydraulic Piston on te bottom of a hill

    At a ride in an amusement part a cart, with a mass of 150 kg, rolls down a long curved hill. The height of the hill is 50 m and the length of the track that the cart follows is 300 m. As the cart rolls down the hill, it experiences both a rolling frictional force and air resistance. The net...
  11. J

    Piston pushed in a cylinder

    [b]1. How far must a 2.0-cm-diameter piston be pushed down into one cylinder of a hydraulic lift to raise an 8.0-cm-diameter piston by 20 cm? Homework Equations [b]3. what equations do i use is it pV=nRT
  12. M

    Solving the Piston Problem: Calculating Time for No Molecules Left

    Hello, Piston question,i need to work out the time when no molecules are left in the gaseous system.. I have worked out the relative velocity..if i multiply that by the mean free path to get the diffusion coefficient am i getting any closer to the answer? I can work out the change in time...
  13. A

    Pressure inside a chamber with a piston

    :mad:Homework Statement A vertical cylinder of cross-sectional area .07 m^2 is fitted with a tight-fitting, frictionless piston of mass 30 kg. The acceleration of gravity is 9.8 m/s^s. If there are 1 mol of an ideal gas in the cylinder at 395 K, find the pressure inside the cylinder. (Assume...
  14. 5

    Looking for piston details explained

    I'm trying to find an article or something similar online that has a diagram of a piston and explains the different parts of the piston. For example, trying to find out what the piston's compression height, ringland, deck thickness, ring grooves, etc. I would like to know what all of these...
  15. 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...
  16. M

    Piston Compressing a Spring

    Homework Statement A horizontal piston is attached to a spring with a spring constant of 1500N/m. The cross sectional area of the cylinder is A=10cm^2, it contains 0.0040mol of gas. At 20 deg Celsius the spring is neither compresssed nor stretched. How far is the spring compressed, x, if the...
  17. J

    Torque difference: steam turbine vs. piston?

    Hi, I was told that there was an inherent torque advantage to using a piston design over a turbine design (in this case for steam). I said I doubted there was any theoretical reason why this would be true, it would all depend on the design of the engine. My argument was that most turbines in...
  18. A

    Ideal gas in a cylinder closed by a piston connected to a spring

    A cylinder is closed by a piston connected to a spring of constant 2.00 X 10^3 N/m. With the spring relaxed, the cylinder is filled with 5.00L of gas at a pressure of 1.00 atm and a temperature of 20.0ºC. A) If the piston has a cross-sectional area of 0.0100 m^2 and neglible mass, how high will...
  19. S

    Thermodynamic Piston problem.

    A cylinder contains 1kg of saturated H20 at 30C. This piston has a cross-sectional area of .065m^2, a mass of 40kg, and rests on stops. With the piston in this position, the volume of the H20 is .1m^3. The external atmospheric pressure is 94Kpa and g is 9.75m/s^2. Heat is transferred to the...
  20. quasar987

    Thermodynamics piston problem

    A cylindrical container 80 cm long is separated in two compartments by a thin piston, originally held 30cm away from the left side of the piston. The left compartment is filled with 1 mol of an helium gaz at a pressure of 5 atm; the right compartment is filled with Argon at a pressure of 1 atm...
  21. J

    Cylinder with moving piston as air moves in spring contracts

    I have a question with a horizontal cylinder with a piston attached to a spring inside the cylinder. air is then let into the cylinder and the spring contracts increasing the volume. the diameter of the piston is given (10cm), the spring force is given (80KN/m), the initial volume is given...
  22. D

    Force pushing against piston in car engine

    Hi, I've done a bit of research to find my answer, but I haven't been able to come up with anything. Does anyone know what the average amount of force pushing against the piston in a car engine when the explosion occurs? I know it probably differs greatly with the car, but if anyone knows...
  23. G

    Work done as air expands in piston with spring

    There's a problem in my thermo class that I think I have the right answer for, but the value I get doesn't seem to make sense. The problem reads: Warm air is contained in a piston-cyliner assembly oriented horizontally. The air cools slowly from an intial volume of .003 m^3 to a final volume...
  24. A

    Force must be applied to the small piston to lift the engine?

    In a machine shop, a hydraulic lift is used to raise heavy equipment for repairs. The system has a small piston with a cross-sectional area of 0.057m^2 and a large piston with a cross-sectional area of 0.208m^2. An engine weighing 2900N rests on the large piston. What force must be applied to...
  25. L

    Find load with jack and piston

    A hydraulic jack has a pump piston of diameter 0.650cm, and a load piston of 4.40cm. Find the load which can be lifted if a force of 500.N is exerted on the pump piston. Would you use the equation Fd=F(2)d(2)? So (0.00650m)(500.N)=F(.0440m) =73.9N
  26. C

    Internal Energy: gas inside piston

    A cylinder (cross section is 0.2m2) with a free moving piston is filled with gas. The piston is attached to a heavy weight W = 10000N. Outside the cylinder, the air is at 300K and 1atm. Initially the gas is at 300K, then it is heated to 400K. The heat capacity of the gas under the constant...
  27. D

    C Theatres: Where Movie Magic Happens

    A piston pump having a barrel of effective volume 100cm3 is used to exhaust a vessel of volume 2.5x(10^3)cm3. If the initial pressure in the vessel is 1 atm, estimate the reduction in pressure produced by two strokes of the pump, assuming that all processes are isothermal and that air behaves as...
  28. S

    Sound Waves of Piston: Calculation & Amplitude

    I posted this in general physics forum but in retrospect I think I should have posted it here. Since piston compresses and decompresses a gas, it must be generating sound waves. Lets take a small engine with piston stroke 86mm, RPM 8000. An 8000 RPM means it is making 133.333 revolutions...
  29. S

    Sound Intensity of Piston in Engine at 8000 RPM

    consider a piston in an engine with a stroke of 86 mm and RPM 8000 which gives the frequency of sound it is producing(due to compression and decompression) to be 133 Hz and wavelength 2.57 m. Then the pressure amplitude turns out to be 20000 Pa and the intensity of the sound wave to be...
  30. V

    Oscillations of a Piston in a cylinder containing a trapped gas

    A frictionless cylinder of cross-sectional area A contains a gas that is trapped by a piston of mass m that fits the cylinder tightly but is free to move up and down. It is open to atmospheric pressure (PA) on one end. The piston is slightly displaced and when released oscillates about its...
  31. S

    Oil between the piston and the casing manage to move with the piston?

    How does the oil between the piston and the casing manage to move with the piston? Is their no leak of the oil? And does the piston ring actually rub against the walls of the casing? Doesn't it generate too much friction? Does anyone know a good site where they show how the dimensions of...
  32. I

    Calculating Piston Speed in Single Cylinder Engines

    how do you calculate piston speed with a single cylinder engine no transmission what I am trying to do is determine the influence of rod length in that problem
  33. S

    Calculating Pressure for a Hydraulic Lift: A Scientific Approach

    Hello! I was wondering if you could help me with a homework problem: The piston of a hydraulic automobile lift is X meters in diameter. What gauge pressure, in pascals, is required to lift a car with a mass of Y kg? I know that a piston is a cylindrical shaped apparatus - however I...
  34. C

    What is the force you need to use on the piston?

    If there is an ordinary sprayer (you know with the piston on one side and a bottle which has liquid inside it and is connected to the piston's tube by a tube which goes inside the liquid) and the air resistance on the piston when you try to push it is given (lets say F) what is the force you...
  35. Clausius2

    Is This New Piston Head Concept Effective?

    I want to share and discuss with every forum posters here a new concept on piston heads, which by the way is not as brainy as you may think. The new concept is concerned with spark ignition engines. Everybody know that combustion process have two main stages in this kind of engines...
  36. C

    Calculating Piston Velocity Using the Law of Cosines

    In an engine, a 7-inch connecting rod is fastened to a crank of radius 3 inches. The clankshaft rotates counterclockwise at a constant rate of 200 revolutions per minute. Find the velocity of the piston when \theta = \frac{\pi}{3} . I know that I have to use the Law Of Cosines. However I am...
  37. R

    Find the maximum frequency for which the block and piston will be in contact

    A block is on a piston that is moving vertically with simple harmonic motion. a)At what amplitude of motion will the block and piston sperate if the period of the piston's motion is 1.18 seconds? b) If the piston has an amplitude of 5.12 cm in its motion, find the maximum frequency for which the...
  38. Q

    Block on piston undergoing simple harmonic motion

    A block rides on a piston that is moving vertically with simple harmonic motion. if the shm has period 1 s at what amplitude of maotion will the block and piston seperate? T= 1 / f 1= 1 / f x= x cos (wt+0) x= x cos( 2 * pi * 1 + 0) where can i go from here?
  39. M

    Solving for Amplitude of a Brick on a Piston with SHM: Help Needed!

    I have no idea why I can not get this question, but here it is: A brick is resting atop a piston that is moving vertically with simple harmonic motion of period 1.19 s. At what amplitude will the brick separate from the piston? I know that once the acceleration is greater than that of...
  40. N

    Calculating Amplitude of Brick Separation from Piston with SHM

    A brick is resting atop a piston that is moving vertically with simple harmonic motion of period 1.08 s. At what amplitude will the brick separate from the piston? I came across this question reviewing for my test next Thursday. Anyway, I can calculate the angular frequency using the...
  41. P

    Chem+Physics: Solving the Piston Puzzle

    this is my webassign question for this week but I'm a little confused about the first part... for part a) shouldn't the ratio just be 1 to 1, since the piston is exactly in the center?? or did i understand that wrong? I'm not all that great at chem especially when it comes to chem and physics...
  42. R

    Cylinder fitted with piston and spring im lost

    A cylinder is fitted with a piston, beneath which is a spring, as in the drawing. The cylinder is open at the top. Friction is absent. The spring constant of the spring is 2900 N/m. The piston has a negligible mass and a radius of 0.023 m. (a) When air beneath the piston is completely pumped...
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