Rigid bar fulcrum Chaitali prabhudesai. Forces The lever consist of two forces: 1) An effort force: which will tend to rotate the bar around the fulcrum

LEVERS DEFINATION:A mechanical lever is a rigid

bar that rotates around a axis or a fulcrum.

Rigid bar

fulcrum

Chaitali prabhudesai

ForcesThe lever consist of two forces:1) An effort force: which will tend to rotate the bar around

the fulcrum 2) An resisting force: which will resist the movement These forces act around a supporting force which

provides for a point of pivot known as the fulcrum

resistanceeffort


ForcesForce Arm: The distance from the effort to the fulcrum is

known as the force armResistance Arm: The distance between the resistance and

the fulcrum is known as the resistance arm

resistance

effortF A R A


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 rockrockfeathers

F AR A


Mechanical AdvantageMechanical Advantage or leverage is

defined as a ratio of force arm to resistance arm

MA=FA/RA

Mechanical Advantage can either be equal to 1, less than 1 or greater than 1 depending upon the type of lever


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 AResistance


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

effortF A

R A


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 arm

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

F A

R A Resistance

effort


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 levers


ExamplesCommon Examples: Class I lever


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

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)


Anatomical ExamplesClass I lever:


Coronal plane

ExamplesCommon Examples: Class II lever:


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

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


Anatomical ExamplesClass II lever:


Anatomical ExamplesCommon Examples: Class III lever:


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

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


Anatomical ExamplesClass III lever:


Anatomical Examples

Documents

Rigid bar fulcrum Chaitali prabhudesai. Forces The lever consist of two forces: 1) An effort force: which will tend to rotate the bar around the fulcrum