Machines

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Answer

types of machines in the body

1. levers 2. pulleys 3. wheel and axle

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functions of a simple machine

1.balance 2 or more forces** 2. provide advantage in force(wrench v screwdriver) 3. provide an advantage in range of linear motion and speed of movement 4. change the effective direction of the applied force(pulley)

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Levers

simples machines w/ 5 components

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components of a lever

1. fulcrum-A-axis of rotation 2. point of force application(f) 3.point of opposing force application(resistance) R 4. moment arm associated with the force(FA). 5. moment arm assocaited with the resistance(RA)

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moment arms

1. are the phsycail connections between the fulcrum and point of force app 2.are measured as th perpendicular distance from the line of action force or resistance to the axis of motion

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Force Moment arm

the perpendicular distance frm the axis of rotation to the line of action of the force

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resistance moment arm

perppendicular distance between the axis of roation and the line of action of the resistive force

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About Levers

1. only act in rotation motion-so the lines of action (F and R) cannot pass through the axis of rotation for motion to occur 2. product of the magntude of the force &moment arm is the rotary effect of that force-moment or torque 3.(F)(FMA)=R(RMA)

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Classify levers

look at-force application, point of resiFirst class leverstance, fulcrum or axis

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first class lever

F-A-R axis is always between the force and resistance arm

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Function 1 of a first classes lever

Balances 2 forces-in current arrangement, it is apparent that force and resitance can be balanced, if the force and the resistance were equal and the distances between the axxis of rotation and the force and resistance are the same

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Function 2 of a first class lever

changes the effective direction of the applied force. If the force is pushing down, it is apparent that the resistive force will go up

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Function 3 of a first class lever

favors speed and ROM, in order for this to be true, we have to alter the abox diagram by moving the axis closer to the applied force-in new configuration-moving the force a small distance will cause resistance to move a greater distance than force

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Function 4 of a first class lever

favors force production-to be true musct move the axis closer to the resitance-force moment arm is considerably longer than resistance moment arm allows a smaller force to move larger load

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Example of a first class lever in the body

neck extention- F-supplied by the neck extensors A-supplied by the spine/skull articulation R-supplied by the weight of the head, considered to act at the center of gravity of the skull

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Second class lever

A-R-F resistance is ALWAYS closer to the acis of rotation the F, meaning force lever arm is always longer than resistance arm, FAVORS FORCE PRODUCTION

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Example of second class lever

Push-up- A-supplied by feet R-supplied by the center of gravity F-supplied by the arms

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Example of a second class lever-heel raise

a-supplied by toes R-supplied by the COG F-supplied by the calf muscles

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Third class lever

R-F-A force is ALWAYS closer to axis- FAVORS speed and ROM due to RMA>FMA

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Example of a third class lever

Elbow flexion R-supplied by the load in the hand F-supplied by the msucle force A-supplied by the elbow

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Pulleys

can be used to create advantages in force, ROM or speed of movement,

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primary functions of a pulley within the body?

1. to change the direction of force applied 2. change the angle of force applied

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how many classes of pulleys are there?

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class 1 pulley

an external support acts as a pully to give improved angle of pull EXAMPLE PATELLA

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Class 2 pulley

action of the muscle at the joint is changed because of the pully ie action of the peroneous longus and brevis, v that of the peroneus tertius on the ankle joint tertius-only df longus/brecvis-wraps post to lat mal whihch changes function to ev and pf

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Class 3 pulley

joint itself servves as the pulley to result in an improved andle of pull EXAMPLE:the condyles of the femur and tibia-help with knee/hip action

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Class 4 pulley

the muscle wraps around the pulley causing the pully to rotate EXAMPLE:pronator teres

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Class 5 pulley

the msucle is its own pulley or uses another msucle as a pulley to improve the angle of pull EXAMPLE:biceps brachii and brachialis-once brachialis swells the angle the biceps brachii changes and makes bicep flexion easier

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Wheel and Axle

rotation of the trunk about the spin- pelvis is the wheel spine is the axle times the wheel will rotate with the axle and sometimes the axle will roatat alone or wheel can rotate about axle favors SPEED and ROM

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