Slide4 Vibration (rotating Equipment)

8/17/2019 Slide4 Vibration (rotating Equipment)

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WAVES AND VIBRATIONS NOTES


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A wave is a vibration moving in time and space

It cannot exist in one place but must

extend from one place to another

Wave motion is a wa to trans!er energ wit"out

transfer of matter


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A vibration is back and forth movement

A single #isturbance or vibration is a wave pulse

I! t"e source repeate#l vibrates it pro#uces periodic motion


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Sound is pro#uce# w"en matter vibrates

Demonstration$ W"at "appens w"en a tuning !or%

is place# in water&

Since soun# is pro#uce# w"en matter vibrates'

soun# is a !orm o! mechanical energ(


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)rest

troug"

mi#point

)rest$ High point in the wave

Troug"$ Low point in the wave

********+i#point o! wave where the wave is in equilibrium

Amplitu#e Distance from the midpoint to the crest or trough

T"e "ig"er t"e amplitu#e t"e stronger the wave


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Wavelengt" is$ the distance from one point on the wave to

the identical point on the next wave.

Crest to Crest, or trough to trough


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,re-uenc is$ How frequentl a vibration occurs.

How man wavelengths or wave ccles pass in one second.

I! . wavelengt"s /or vibrations' or wave ccles0 pass a

point in one secon#' t"en t"e !re-uenc is$! vibrations" second. #$r ! ccles" sec%


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1ert2 is$ a unit of frequenc #abbreviated H&%

It was name# a!ter

1einric" 1ert2

w"o #emonstrate#

ra#io waves in 3445(

One vibration per secon# is one 1ert2(

. vibrations /or waves' or ccles0 per

secon# is ________ 1ert2 2


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DE+ONSTRATIONS$

Hacksaw blade$ /hold blade against table edge.Change length hanging over and vibrate it.

Describe t"e !re-uenc o! vibration an# pitc"

/"ig"ness or lowness o! t"e soun#0 w"en t"e "ac%saw bla#e is long(

Longer vibrations, so lower sound Describe t"e !re-uenc o! vibration an# pitc" w"en t"e

"ac%saw bla#e is s"orter(

Higher vibrations so higher pitch


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Containers with water( /pop bottles

to blow across or crstal glass to rub

!inger aroun#0

W"at is t"e relations"ip between t"e amount o! water

in eac" container an# t"e pitc"&

Less water vibrating means higher pitch.

'ore water vibrating is lower pitch

T"e longer t"e lengt" o! vibrating air above t"e water'

t"e Lower t"e pitc" when blowing into a bottle


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I! a wave6s !re-uenc is %nown' t"en ou can calculate

t"e period o! time it ta%es !or one wave to pass(

I! t"e !re-uenc is . 12' t"en t"e time it ta%es !or

3 vibration is ( second (

Explain t"e relations"ip between 7erio# an# ,re-uenc$

)requenc * + eriod * +

eriod #-% )requenc t is an inverse relationship

f freq * / H& then eriod * +"/ or .! seconds


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T"e Sears Buil#ing in

)"icago swas bac% an# !ort"

at a vibration !re-uenc o! 8(3 12(W"at is its 7erio# o! vibration&

- * + " f

+ " 0.+ ccles"sec * +0 seconds"ccle

t takes +0 seconds for it to swa back

and forth one time


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WAVE S7EED

Spee# o! a wave #epen#s on t"e me#iumt"roug" w"ic" t"e wave travels(

Spee# #epen#s on$

3( Densit o! materials how man molecules there

are to bump into each other .( Elasticit how well it changes shape and then

springs back. 'ore elastic, the faster the

waves travel.

9( Temperature higher the temperature,

the faster the molecules move

Soun# travels about 998 m:s * 9;8 m:s #epen#ing on t"e temperature o!

t"e air( It travels < times !aster in water' an# 3; times !aster in steel(


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Wave Spee# = frequenc x wavelength

λ 1reek letter Lambda * wavelength

Wave Speed Freq. λ


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Soun# Waves

,re-uenc /120 Wavelengt" /m0 Wave Spee# /m:s0358 .(39 9 95 8(45 9


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I! a water wave vibrates up an# #own . times eac"

secon# an# t"e #istance between wave crests is 3(; meters'

w"at is t"e !re-uenc o! t"e wave&

W"at is its wavelengt"& W"at is its spee#&

) * ! H& 2avelength * +./ m

Speed * ! ccles x +./ m = 3 m"sec

Sec Ccle


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W"at is t"e wavelengt" o! a 9


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TRANSVERSE WAVES

'otion of the wave is at right angles to the direction of travel

Examples$ waves on the surface of liquids,

8adio waves, light waves

slink demo


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?ON@ITDINA? WAVES

motion of waves is in the same direction


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Examples$ sound waves

SM!" #$%&S


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'ransverse

(ongit)dinal

co*pression

rare+action

S #"-$"W F 'H" W-" '/"S


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NATRA? ,REEN)C$

W"en ou #rop a wrenc" an# baseball bat on t"e

!loor' ou "ear . #i!!erent soun#s( T"e vibrate#i!!erentl( W"en an obect compose# o! an elastic

material is #isturbe# it vibrates at its own special set

o! !re-uencies( T"is nat)ral +req)enc0 #epen#s on

!actors suc" as$

elasticit and the shape of the ob9ect

RESONAN)E$

W"en t"e vibration o! one obect causes anot"er obect to$

vibrate at its natural frequenc

A #ramatic increase in :mplitude occurs(


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Examples o! Resonance

Swinging on a swing pump in

rhthm with natural frequenc of theswing, go higher and higher

Tuning !or% can cause another to vibrate

Tacoma Narrows Bri#ge

destroed b a 40 mph wind (video)

Wine glass s"attering

http://www.acoustics.salford.ac.uk/feschools/waves/wine1video.htmhttp://www.acoustics.salford.ac.uk/feschools/waves/wine1video.htm


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$%'"#F"#"%C" F W-"S

)onstructive Inter!erence$ when one wave crestoverlaps another crest and the build together

Animation courtes o! Dr( Dan Russell' ettering niversit


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Destructive Inter!erence$ when one wave crest

overlaps a trough and the cancel each other out.

;S


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SHW M$#" /''"#%S


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Stan#ing Waves$ when wave is reflected back

exactl opposite to the original wave

A = anti*no#e B = no#e



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Beats$ periodic variation in loudness of sounds

caused when ! slightl different frequencies are

sounded together

I! one tuning !or% vibrates at .5< 1ert2' an# t"e

ot"er at .5. 1ert2' t"en t"e are Fin stepG . times

eac" secon#( A beat !re-uenc o! 2 h1 is "ear#(


#emo

http://library.thinkquest.org/19537/java/Beats.htmlhttp://library.thinkquest.org/19537/java/Beats.html


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T1E DO77?ER E,,E)T$

T"e Doppler e!!ect is a c"ange in frequenc of a

wave due to the motion of the source or receiver.


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Doppler E!!ect occurs !or visible lig"t too(

S"ort lig"ts waves are >lue an#

?ong wavelengt"s are 8ed

Astronomers can measure w"et"er stars an# galaxies are

moving towar# us or awa !rom us b loo%ing at t"e

lig"t s"i!t(

Blue S"i!t means * the light is coming faster ?

stars are moving forward

Re# S"i!t means* the star is going awa

T"e can calculate t"e spee# o! a spinning star(

T"ere is a blue s"i!t on t"e si#e spinning towar# us

an# a re# s"i!t on t"e si#e spinning awa(


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7olice use t"e Doppler e!!ect o! ra#ar to #etermine

t"e spee# o! a car( A computer in t"e ra#ar guncompares t"e !re-uenc o! t"e ra#ar emitte# b

t"e antenna wit" t"e

frequenc of the reflected waves.


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OS)I??OS)O7E$ : device that is used to measureelectrical signals as waves. t shows the strength of the

wave #amplitude% and the period of time between

each wave. @ou can then calculate the frequenc

of the waves

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