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LEVERS LEVERS

LEVERS - PowerPoint Presentation

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Uploaded On 2016-04-24

LEVERS - PPT Presentation

DEFINATION A mechanical lever is a rigid bar that rotates around a axis or a fulcrum Rigid bar fulcrum Chaitali prabhudesai Forces The lever consist of two forces An effort force which will tend to rotate the bar around the fulcrum ID: 291298

resistance effort chaitali prabhudesai effort resistance prabhudesai chaitali fulcrum levers force lever examples class lies anatomical part advantage arm

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Slide1

LEVERS

DEFINATION:A mechanical lever is a rigid bar that rotates around a axis or a fulcrum.

Rigid bar

fulcrum

Chaitali prabhudesaiSlide2

ForcesThe lever consist of two forces:An effort force: which will tend to rotate the bar around the fulcrum

An resisting force: which will resist the movementThese forces act around a supporting force which provides for a point of pivot known as the fulcrum

resistance

effort

Chaitali prabhudesaiSlide3

ForcesForce Arm: The distance from the effort to the fulcrum is known as the force arm

Resistance Arm: The distance between the resistance and the fulcrum is known as the resistance arm

resistance

effort

F A

R A

Chaitali prabhudesaiSlide4

Law Of LeverIn order for the lever to be in equilibrium:Load(resistance) * Load Arm= Effort * Effort ArmE.g. 1 gm of feather has to be balanced by 1 kg of rock

rock

feathers

F A

R A

Chaitali prabhudesaiSlide5

Mechanical AdvantageMechanical Advantage or leverage is defined as a ratio of force arm to resistance arm

MA=FA/RAMechanical Advantage can either be equal to 1, less than 1 or greater than 1 depending upon the type of leverChaitali prabhudesaiSlide6

Types Of LeversClass I Levers: In these types of levers the fulcrum lies between the resistance and the effort

The Mechanical advantage for these levers can be equal to 1,>1 or < 1 depending upon the position of the fulcrum.

effort

F A

R A

Resistance

Chaitali prabhudesaiSlide7

Types Of LeversClass II levers: In these types of levers the resistance lies between the fulcrum and effort.Thus the effort(force) arm is always greater than the resistance arm

Mechanical Advantage: Thus the mechanical advantage of this lever is always greater than 1

Resistance

effort

F A

R A

Chaitali prabhudesaiSlide8

Types Of LeversClass III levers: In these types of levers the effort lies between the fulcrum and resistance.Thus the resistance arm is always greater than the force armMechanical Advantage: Thus the mechanical advantage of this lever is always less than 1

F A

R A

Resistance

effort

Chaitali prabhudesaiSlide9

Levers In Human BodyIn human body the bones act as levers, the weight of that body part acts as the resistance and the associated muscular contraction(muscle attached to that bone) acts as the effort. Motion is produced only when the effort exceeds the resistance .

For your legs or any other body part to move the appropriate muscles and bones must work together as leversChaitali prabhudesaiSlide10

ExamplesCommon Examples: Class I lever

Chaitali prabhudesai

Scissors: The fulcrum lies at the center, we apply force at the handles of the scissor, the resistance is at the other endSlide11

Anatomical ExamplesOur head is connected to the spine at the atlanto- occipital joint(fulcrum).A coronal plane passing through the body divides the head into a greater anterior part and a smaller posterior part, such the weight of the anterior part is greater than the posterior part

Thus the anterior part of the head tends to fall (bend)forwards(Load) This bending action is prevented by weight of the posterior part of the head and occipital muscles (effort)Chaitali prabhudesaiSlide12

Anatomical ExamplesClass I lever:

Chaitali prabhudesai

Coronal planeSlide13

ExamplesCommon Examples: Class II lever:

Chaitali prabhudesai

The fulcrum lies at one end ,the load is present at the center, and the effort force is applied at the other endSlide14

Anatomical ExamplesClass II Lever: When we raise our body on the toes ,the toes act as the fulcrum, the weight of the body acts as the resistance force and the calf muscles act as the effort force

Chaitali prabhudesaiSlide15

Anatomical ExamplesClass II lever:

Chaitali prabhudesaiSlide16

Anatomical ExamplesCommon Examples: Class III lever:

Chaitali prabhudesai

Forceps:The fulcrum lies at one end, the effort force lies at the center ,the resistance force lies at the other endSlide17

Anatomical ExamplesClass III Lever: When we hold a object in our hand the object acts the load, the elbow joint acts as the fulcrum and the muscles in the arm(Biceps) act as the effort force. Generally most of the levers in the human body are class III levers

Chaitali prabhudesaiSlide18

Anatomical ExamplesClass III lever:

Chaitali prabhudesaiSlide19

Anatomical Examples