Answer Key Dynamics of Machinery

8/12/2019 Answer Key Dynamics of Machinery

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ANSWER KEY FOR PART A

1. The inertia force is an imaginary force, hich hen acts !"on a rigi# $o#y, $rings it

an e%!i&i$ri!m "osition. 't is n!merica&&y e%!a& to the acce&erating force in magnit!#

$!t o""ositein #irection.

(athematica&&y, 'nertia force ) Acce&erating force ) m.a

Where m ) (ass of the $o#y, an# a) *inear acce&eration of the centre of gra+ity

the $o#y.

. -A&em$ert/s "rinci"&e states that the res!&tant force acting on a $o#y together

the re+erse# effecti+e force 0or inertia force are in e%!i&i$ri!m.

2. The t!rning moment #iagram 0a&so 3non as cran3 effort #iagram is the gra"hic

re"resentation of the t!rning moment or cran3effort for +ario!s "ositions of the cran

't is "&otte# on 4artesian coor#inates, in hich the t!rning moment is ta3en as t

or#inate an# cran3 ang&e as a$scissa.

5. 't is #efine# as the ratioof the ma6im!m f&!ct!ation of energy to the or3 #one "

cyc&e.

7. The "rocess of "ro+i#ing the secon# mass in or#er to co!nteract the effect of the

centrif!ga& force of the first mass is ca&&e# $a&ancing of rotating masses.

8. 'f rotating "arts are not "ro"er&y $a&ance#, the #ynamic forces are set !". The

forces not on&y increase the &oa#s on $earings an# stresses in the +ario!s mem$e

$!t a&so "ro#!ce !n"&easant an# e+en #angero!s +i$rations. 'n or#er to minimi

"ress!re on the main $earings hen an engine is r!nning, the rotating "arts sho!

$e $a&ance#.

:. The ma6im!m magnit!#e of the !n$a&ance# force a&ong the "er"en#ic!&ar to the &i

of stro3e is 3non as hammer $&o.

;. The res!&tant !n$a&ance# force #!e to the to cy&in#ers, a&ong the &ine of stro3e,

3non as tracti+e force.


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1=. Free or nat!ra& +i$rations .When no e6terna& force acts on the $o#y, after gi+ing it

initia& #is"&acement, then the $o#y is sai# to $e !n#er free or nat!ra& +i$rations.

Force# +i$rations.When the $o#y +i$rates !n#er the inf&!ence of e6terna& force, th

the $o#y is sai# to $e !n#erforce# +i$rations

11. The s"ee# at hich the shaft r!ns so that the a##itiona& #ef&ection of the shaft fro

the a6is of rotation $ecomes infinite is 3non as critica& or hir&ing s"ee#.

1. The ratio of the act!a& #am"ing coefficient to the critica& #am"ing coefficient is 3no

as #am"ing factor or #am"ing ratio.

12. 't is the ratio of ma6im!m #is"&acement of the force# +i$ration 06 ma6 to the #ef&ecti

#!e to the static force F 06o.

15. When a machine is s!""orte# $y a s"ring, the s"ring transmits the force a""&ie#

the machine to the fi6e# s!""ort or fo!n#ation. This is ca&&e# transmissi$i&ity.

17. When an !n$a&ance# machine is insta&&e# on the fo!n#ation, it "ro#!ces +i$ration

the fo!n#ation. So in or#er to "re+ent these +i$rations or to minimi9e the transmissi

of forces to the fo!n#ation, +i$ration iso&ation is im"ortant.

18. The materia&s !se# for +i$ration iso&ation are "a#s of r!$$er, fe&t or cor3 an# meta

s"rings.

1:. The f!nction of a go+ernor is to reg!&ate the mean s"ee# of an engine, hen the

are +ariations in the &oa#.

1;. The sensiti+eness is #efine# as the ratio of the #ifference $eteen the ma6im!m a

minim!m e%!i&i$ri!m s"ee#s to the mean e%!i&i$ri!m s"ee#.

1


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ANSWER KEY: PART-B

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26)

When the rotation of the rotor is c&oc3ise hen &oo3ing from the &eft 0 i.e. rear en# or stean# hen the $o is rising 0i.e. "itching is !"ar#, then the reacti+e gyrosco"ic co!"&e acts in tc&oc3ise #irection hich ten#s to t!rn the $o toar#s right 0 i.e. toar#s star$oar#.Ans.


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PART- B STEP MARK SPLIT UP

21) 12 MARKS

Ste" (ar3 S"&it >"

Press!re on s&i#e $ars, 2 marThr!st in the connecting ro#, 2 marTangentia& force on the cran3"in, 2 marT!rning moment on the cran3 shaft. 2 mar

22) 12 MARKS

Ste" (ar3 S"&it >"

(agnit!#es 8 marAng!&ar "ositions 8 mar

23) 12 MARKS

Ste" (ar3 S"&it >"

4ritica& #am"ing coefficient, 2 mar-am"ing factor, 2 mar*ogarithmic #ecrement, 2 marRatio of to consec!ti+e am"&it!#es 2 mar

24) 12 MARKS

Ste" (ar3 S"&it >"

Stiffness of each s"ring 5 mar-ynamicforce transmitte# to the $ase 5 marNat!ra& fre%!ency of the system 5 mar

25) 12 MARKS

Ste" (ar3 S"&it >"

(inim!m s"ee# 5 mar(a6im!m s"ee# 5 marRange of s"ee# 5 mar


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26) 12 MARKS

Ste" (ar3 S"&it >"

(a6im!m gyrosco"ic co!"&e 5 mar(a6im!m ang!&ar acce&eration of the shi" #!ring "itching, 5 mar-irection 5 mar

27) 12 MARKS

?ase# on the com"&etion of the #eri+ation, mar3 i&& $e aar#e#

28) 12 MARKS

Ste" (ar3 S"&it >"

(a6im!m f&!ct!ation of energy 8 mar(ass of the f&yhee& 8 mar

Answer Key Dynamics of Machinery

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