# conversion of P.E to K.E?

Discussion in 'Mechanical | Automobile | Aeronautics' started by viratvicky, Aug 2, 2012.

### viratvickyApprentice

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how pressure energy is converted into kinetic energy???

### zaveriStar

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When a fluid exits from a nozzle, its pressure is reduced and velocity is increased. maybe that is how the kinetic energy increases , because kinetic energy has velocity components in it.

K.E = 1/2 m*v(square), and v is velocity of the fluid

### viratvickyApprentice

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sir,

And also one doubt sir, when fluid passes through nozzle at its end nozzle area is less and then how pressure increases? because we have the equation p=F/A here p is inversly to pressure

### A.V.RamaniMentor

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It is very important to get the concepts right. How on earth did you get the idea of inverse proportionality? The very term KE indicates the dependence on velocity. To take your idea to an absurd level, KE should become infinity at zero velocity!

The relationship is KE = 0.5mV^2, which means that KE is proportional to the square of the velocity.
If the velocity doubles KE increases four times.
You might have got confused by writing the equation as :K.E=1/2mv^2. This means (1/2) x (mV^2).
Better to think as KE = 0.5mV^2 to avoid confusion.
http://www.codecogs.com/reference/engineering/fluid_mechanics/pipes/venturi_meters.php

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I think you should learn Bernoulli's principle from any fluid mechanics book.

### Khartz DiCertified CEan

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From Bernoullis principle in fluid dynamics, it states that for an inviscid flow,an increase in the speed of the fluid occurs simultaneously with a decrease in pressure,or the decrease in the fluid potential energy.That is energy is conserved(transfered from one form to another),,,

### IssueStar

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I would recommend, all the interested people to apply KE not equal to PE principle to vibrating bodies for example study the effect of oscillations setup in a mercury column ( Hg height increasing and decreasing in manometer). Just see the kind of mathematical errors you get. .
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### A.V.RamaniMentor

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In a sense vibrating bodies are perfect examples for interchangeability of PE and KE. These bodies are undergoing simple harmonic motion. In vacuum and absence of friction they go on oscillating continuously.
The mercury in one limb rises up to a maximum height, stops and reverses. The mercury reaches the lowest point in the fall and stops again. The difference in the two levels is the change in PE. If one could measure the speed at different points it will be seen that the maximum speed is at the mid point of the two levels.

### IssueStar

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Yes, then the equation reduces to a simple case of mass, damper and spring stiffness. One can easily find the resonant frequency and all the vibrating parameters. Like vibrating bodies there are number of examples where we get interesting outputs equating K.E to PE.

### A.V.RamaniMentor

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Issue, you have given the best example of conversion of PE to KE with the simple harmonic motion.

### viratvickyApprentice

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oh! Yes it's directly proportinal....i did a mistake when typing.

### viratvickyApprentice

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oh! Yes its directly proportionl. I did a mistake when typing.

### IssueStar

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