lever

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LEVERS
Dr. KauShik Patel (PT)

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What is Lever:-
A lever is a rigid bar which is capable of
movement about a fixed point called a FULCRUM

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Work is done when a force or effort (E), applied at one
point on the lever, acts upon another force or weight(W),
acting at a second point on the lever.
Effort Arm (EA) :-
The perpendicular distance from the fulcrum to the
effort is called
Weight Arm (WA) or Resistance arm (RA):-
The perpendicular distance from the fulcrum to the
weight is called

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In the body lever is represented by the bone,
which is capable of movement about a fulcrum
form at the articulating surface of a joint.
The effort which is works the lever is supplied by
the force of muscular contraction, applied at the
point of insertion.
While the resistance may either a center of
gravity of the part moved or weight of the object
to e lifted

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TYPES OF LEVERS :-
There are three types of lever
1st order
2nd order
3rd order

6. First order lever
 In this F lies in between the point of application of
EF and the point of application of RF.
3 possibilities:
1) EA=RA EA RA
E F R
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7. 2. EA > RA
EA RA
E F R
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8. 3. RA > EA
EA RA
E F R
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Second order levers-
In this the RA has a point of application between the F and
the point of application of the EA. (EA>RA)
EA
E R F
RA

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Third order lever –
In this the EA has a point of application between the F and
the point of application of the RA. (RA>EA)
RA
F E R
EA

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Levers in BODY :-
 First Order Lever – Head Nodding
 Second Order Lever – Brachioradialis muscle
 Third Order Lever – Brachialis

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13. Lever at home and at work
1st order –seesaw, tack lifter, scissor.
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14.  2nd order- wheel barrow,door
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15. 3rd order – sugar tongs or foreceps
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MECHANICAL ADVANTAGE :-
It is ratio of effort arm to resistance arm.
The length of effort arm exceeds that of the
resistance arm less effort will be required to achieve result
and advantage will be gained by the use of the lever.

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Measure of efficiency of.
If the EA= RA - no advantage is gained
If the EA > RA - advantage is gained
If the EA< RA - no advantage is gained
In first order lever MA is gained when the F is near to W
All in second order lever
Never obtained in third order

18. Thank you….
levers