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PRESENTED BY
SANJAY KUMAWAT
DESIGN OFLEVERS
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WHAT IS LEVER
A lever includes a stif structure (the lever)that rotates around a xed point called theulcrum.
OR
A Lever is rigid rod or bar capable o turningabout a xed point called ulcrum
U!" A A #$% &O L'& LOA" * #ALL
!OR&.
fulcrum
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ANATOMY OF THELEVER
Lever + A bar that is ree to move about axed point
,arts o a lever
ulcrum +&he xed point o a lever
!fort Arm +&he part o the lever that theefort orce is applied to (measured rom
the ulcrum to the point at -hich the orceis applied)
Resistance Arm +&he part o the lever thatapplies the resistance orce (measured
rom the ulcrum to the center o the
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ANATOMY OF THELEVER
Levers may be straight or curved
Forces applied on the lever parallel or inclined
Effort arm load arm
Large load- small effort i.e. l2should be effort arm and it should
be greater than l1.
Large effort arm may not be possible due to space limitations.
For greater leverage compound levers (straight pieces with
pins
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APPLICATION OF LEVERS IN ENGINEERINGPRACTICE
Three Classes of LeversFirst Class f!l"r!#
$et%ee& I&'!t a&( o!t'!t
Se"o&( Class ) o!t'!t$et%ee& f!l"r!# a&(
i&'!t Thir( Class ) i&'!t
$et%ee& f!l"r!# a&(
o!t'!t
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FIRST CLASS LEVERS
FIRST CLASS LEVERS ) *SEESAW+ LEVERSst%lass Lever /&he ulcrum is located bet-eenthe efort arm and the resistance arm.
irst class levers can multipl0 orce and distance
!xamples1 scissors2 see/sa-2 hammer3s cla-s2 pliers2 etc4
L2 effort arm > L1- load arm
Mechanical advantage is more than one
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FIRST CLASS LEVERS
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SECOND CLASSLEVERS
,ND
CLASS LEVERS ) *WHEEL-ARROW LEVERS+5nd%lass Lever / resistance is located bet-eenthe efort arm and the ulcrum. &hese leversmultipl0 the orce but the direction sta0s the
same.!xample1 -heelbarro-2 stapler2 bottle opener2nger nail clippers2 nut crac6er
L2 effort arm > L1- load armMechanical advantage is more than one
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SECOND CLASSLEVERS
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THIRD CLASSLEVERS
L2 effort arm < L1- load arm
Mechanical advantage is less than one
ot recommended in
engineering practice
7rd%lass Lever /&he efort orce is located bet-eenthe ulcrum and the resistance. &he efort arm isal-a0s shorter than the resistance arm so it cannotmultipl0 the orce and the #A is al-a0s less than .
!xamples1 ra6e2 hoc6e0 stic62 broom2 shovel2 shing pole2t-ee8ers2 tongs
.RD
CLASS LEVERS *TWEE/ERS+
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THIRD CLASSLEVERS
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ANALYSIS TO SIMPLEMACHINE
!he castings must be lifted 2"" mm
FORCE ML!"#L"ER R$!"O %MEC&$'"C$L $()$'!$*E+
#n the lever system shown in figure $ above% the load being lifted is about
three times more than the effort being applied. !he load divided by the effort
gives a ratio. !his ratio is a force multiplier% or how much more load can belifted compared to the effort.
!he lever in figure therefore has a force-multiplier ratio of 2.&& (a ratio has no
units of value'.
. EFFORT = 260 N
LOAD = 750 N
600 mm
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ANALYSIS TO SIMPLEMACHINE
Example 1
Find the force-multiplier ratio for the lever in figure above.
Force-multiplier ratio load
effort
)*"
2+"
2.&&
EFFORT = 260 N
LOAD = 750 N
600 mm
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ANALYSIS TO SIMPLEMACHINE
Find the distance-multiplier ratio leverage for the lever in figure $ above.
,ovement-multiplier ratio distance moved by the effort
distance moved by the load
+"" mm
2"" mm
EFFORT = 260 N
LOAD = 750 N
600 mm
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ANALYSIS TO SIMPLEMACHINE
Example
Find the efficiency of the lever system shown in figure $.
Efficiency (' Force /atio 1""
,ovement /atio
2.&& 1"" 0+%
!he system shown in figure has an efficiency of nearly 1"" per cent. o
system can be 1"" per cent efficient there are always losses. !he losses in a
lever system consist of energy lost to friction at the fulcrum of the lever andthe energy lost in strain as the lever bends slightly. #n some cases a small
amount of energy will also be lost in the form of sound.
Remem,er no machine is 1.. /er cent efficient0 Common
energ losses include heat energ due to friction strainener and sound ener 0
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DESIGN OFLEVERS
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DESIGN OFLEVERS
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DESIGN OFLEVERS
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DESIGN OFLEVERS
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DESIGN OFLEVERS
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CROSS SECTION OF LEVERARM
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CROSS SECTION OF LEVERARM
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CROSS SECTION OF LEVERARM
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E0AMPLE
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E0AMPLE
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E0AMPLE
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E0AMPLE
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TYPES OFLEVERS
10 &$'( LE)ER
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TYPES OFLEVERS
20 FOO! LE)ER
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TYPES OFLEVERS
30 CR$'4E( LE)ER
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TYPES OFLEVERS
50LE)ER FOR $ LE)ER $FE!6 )$L)E
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TYPES OFLEVERS
70 8ELL CR$'4 LE)ER
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O-1ECTIVE
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O-1ECTIVE
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O-1ECTIVE
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O-1ECTIVE
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O-1ECTIVE
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O-1ECTIVE
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O-1ECTIVE
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O-1ECTIVE
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THAN2 YO3
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