Levers in the Body

Levers in the BodyFirst- flesh LeversTypical examples of commencement- separate jimmy are the crowbar, seesaw, and cubitus ex emphasis. An example of this lawsuit of prise in the corpse is seen with the triceps applying the extort to the olecranon (F) in extending the nonsupported fore build (W) at the cubitus (A). Other examples of this type of pry whitethorn be seen in the soundbox when the agonist and the antagonist musclebuilder builder groups on all side of a joint bloc vertebra are contracting simultaneously with the agonist producing wedge while the antagonist supplies the resistance. A first-class prise is designed basically to produce balanced feedments when the axis is midway amongst the exponent and the resistance. When the axis is jam to the impel, the lever produces despatch and range of doing (triceps in elbow extension). When the axis is close to the resistance, the lever produces big businessman motion (crowbar).In applying the principle of le vers to the remains it is nearly-valuable to remember that the line-out is employ where the muscle inserts in the bone and not in the belly of the muscle. For example, in elbow extension with the shoulder fully flexed and the gird beside the ear, the triceps applies the force to the olecranon of the ulna behind the axis of the elbow joint. As the utilise force exceeds the amount of fore section resistance, the elbow extends.This type of lever may be variegated for a given joint and muscle, depending on whether the remains segment is in contact with a surface such as a underprice or wall. For example, we have demonstrated the triceps in elbow extension being a first-class lever with the lot free in space where the arm is pushed upwards away from the remains. By placing the hand in contact with the floor, as in performing a push-up to push the body away from the floor, the same muscle action at this joint now changes the lever to second class because the axis is at the h and and the resistance is the body weight at the elbow joint.In a first class lever, the weight and force are on opposite sides of the fulcrumA small force can be utilize to advantage over a heavy weight if a abundant force armor lever arm can be used. Examples of this lever include scissors, crowbars, andteeter-totters.An example of a first-class lever is the joint between the skull and the atlasvertebrae of the spine the spine is the fulcrum across which muscles lift the capitulum.Here the fulcrum lies between the attack and the committal. In our bodies, a lever of the first class can be found when the head undergoes nodding movements, i.e. when the occipital condyles articulate with the facets of the atlas. The weight of the face and the head are the resistance. The compressing of the neck muscles is the drift to lift the weight. Another example of a lever of the first class is when the bent arm is trueened . A lever of the first class serves a 2fold purpose, i.e. it ste p-ups the drive of movement and it get acrosss the resistance. In doing so, the resistance (load) is moved in the opposite direction.http//www.botany.uwc.ac.za/Sci_Ed/grade10/ universephys/images/man/1_class.gifLever of the first classSecond Class LeverThis type of lever is designed to produce force meovements, since a lage rsistance can be moved by a relatively small force. An example of a second-class lever is a wheelbarrow. Besides the example given before of the triceps extending the elbow in a push-up another confusable example of a second-class lever in the body is plantar flexion of the creation to raise the body up on the toes. The ball of the foot (A) serves as the axis of rotation as the ankle plantar flexors apply force to the calcaneus (F) to lift the resistance of the body at the tibial adjunction (W) with the foot. in that respect are relatively few occurrences of second-class levers in the body.In the second class lever, the load is between the fulcrum and the forceA smaller trial can be used to advantage over a larger weight. An example ofthis lever is a wheelbarrow.An example in the human being body of a second-class lever is the Achillestendon, pushing or pulling across the heel of the foot.Here the load lies between the fulcrum and the effort. A lever of the second class operates on the same principle as a wheelbarrow. A small upward force applied to the handles can castigate a much larger force (weight) acting take inwards in the barrow. Similarly a relatively small muscular effort is required to raise the body weight. In our bodies, a lever of the second class can be found in our feet when we stand on our toes and lift our heels of the ground. The resistance (load) is the weight of our body resting on the arch of the foot. The effort is brought about by the contraction of the calf muscle attached to the heel. This leverage allows us to walk. The main purpose of a lever of the second class is to overcome the resistance.http//www. botany.uwc.ac.za/Sci_Ed/grade10/manphys/images/man/2_class.gifLever of the second classThird Class LeverWith this type of lever the force being applied between the axis and the resistance, are designedto produce speed and range of motion movements. Most of the levers in the hman body are of thistype, which require a broad deal of force to move even a small resistance. Examples include ascreen door operated by a short spring and application of lifting force to a spadeful handle with thelower hand while the upper hand on the shovel handle serves as the axis of rotation. The bicepsbrachii is a typical example in the body. Using the elbow joint (A) as the axis, the biceps appliesforce at its insertion on the radial tuberosity (F) to go around the forearm up, with its perfume of graveness(W) serve as the stage of resistance application.The brachialis is an example of true third-class leverage. It pulls on the ulna just below the elbow,and since the ulna cannot rotate, the pull is direct and true. The biceps brachii, on the other hand,supinates the forearm as it flexes, so that the third-class leverage applies to flexion only.Other examples include the hamstrings contracting to flex the leg at the knee while in a standing(a)position and using the iliopsoas to flex the thigh at the hip.In the third class lever, the force is between the fulcrum and the loadIn this case, there is no force advantage force is NOT increased. In fact, alarger force is actually needed to move a smaller weight, so there is a forcedisadvantage. The use of this lever is in the extend to in speed of movement of theweight.Examples of this lever class include The inside door handle of a car, the coiledspring pulling on a screen door, a pair of finger-nail clippers, and tweezers.An example of a third-class lever in the human body is the elbow joint whenlifting a book, the elbow joint is the fulcrum across which the biceps muscleperforms the turn over.Here the effort lies between the fulc rum and the load. In our bodies, an example of a lever of the third class is when the biceps contracts, allowing us to lift something in our hand. The elbow is the fulcrum, the hand and its contents are the resistance (or load) and the biceps muscles creates the effort. The load can be moved rapidly over a large outgo, while the block of application moves over a relatively short distance. The main purpose of this type of lever is to obtain rapid movement.http//www.botany.uwc.ac.za/Sci_Ed/grade10/manphys/images/man/3_class.gifLever of the third classMore Information About Levers A Brief ReviewF A lever is characterized by a fulcrum, a force arm and a weightarm.F The force arm is the distance from the fulcrum to the point whereforce is applied.F The weight arm is the distance from the fulcrum to the center ofgravity of the weight. First Class Lever The fulcrum is between the force andthe weight. Second Class Lever The weight is between the fulcrumand the force. Third Class Lever Th e force is located between thefulcrum and the weight.F Most of the movements of the body are produced by third classlevers.F Third class levers give the advantage of speed of movement ratherthan strength.F Second class levers give the advantage of strength.F First Class levers can give the advantage of strength or speeddepending on where the fulcrum is located.F Since the human body is made up mostly of third-class levers, itsmovements are adapted to a greater extent to speed than to strength. (Shortforce arm/long weight arm)http//www.botany.uwc.ac.za/Sci_Ed/grade10/manphys/skel_mus.htmRelationship of the length of lever armsThe resistance arm is the distance between the axis and the point of resistance application.The distance between the axis and the point of force application is known as the force arm.thither is an inverse relationship between force and the force arm just as there is betweenresistance and the resistance arm. The longer the force arm, the less(prenominal) force re quired to move thelever if the resistance and resistance arm bear constant. In addition, if the force and force armremain constant, a greater resistance may be moved by shortening the resistance arm.There is also a proportional relationship between the force components and the resistancecomponents. For movement to occur when either of the resistance components increase, theremust be an increase in one or both of the force components. Even slight variations in the locationof the force and resistance are important in find out the effective force of the muscle.Decreasing the amount of resistance can decrease the amount of force needed to move the lever.The system of leverage in the human body is built for speed and range of movement at theexpense of force. Short force arms and long resistance arms require great muscular strength toproduce movement. In the forearm, the attachments of the biceps and triceps muscles clearlyillustrate this point, since the force arm of the biceps is 1 to 2 inches and that of the triceps lessthan one inch. Many other convertible examples are found all over the body. From a practical point ofview, this means that the muscular system should be strong to supply the necessary force forbody movements, especially in strenuous activity.Most human activity, and especially strenuous activity, involves several levers working together.As with throwing a ball, levers in the shoulder, elbow, wrist, hand, and lower extremities agree to propel the ball. It almost assumes the effect of one long lever from hands to feet. Thelonger the lever, the more effective it is in imparting velocity.Forces in the BodyAthletes boasting some of the wonderful shows of force that the human body is capable of performing.Such force is only possible through the arrangement of the muscles, bones and joints that make up the bodys lever systems. castanets act as the levers, while joints perform as living fulcrums.Skeletal muscles create motion by pulling on unsound co rds of connective tissue called tendons. These tendons in turn pull on the bone which creates motion. Muscles move bones through mechanical leverage. As a muscle contracts, it causes the bone to act like a lever with the joint serving as a fulcrum.Muscle exerts force by converting chemical susceptibility (created during respiration) into tension and contraction. When a muscle contracts, it shortens, pulling a bone like a lever across its hinge.Muscles move and this causes us to move. We are capable of performing a wide variety of movements, hardly, muscle itself moves only by becoming shorter.They shorten and then they rest a muscle can pull but it cannot push.There are almost 700 skeletal muscles of the human body, controlled by a few basic principles involving muscle movements or muscular activity.F Skeletal muscles produce movements by pulling on bones or tendons. The tendon gives a very firm anchorage. The point where a muscle is connected to a bone is called the point of ins ertion.F The bones serve as levers and joints act as fulcrums for the levers. Muscles can only contract a short distance, but since they are attached heartfelt a joint, the movement at the opposite end of a limb is greatly increased. The biceps muscle of the arm may contract only 89 to 90 mm, but the hand pass on move about 60 cm.F The skeletal or voluntary muscles act in pairs rather than singly. One of the muscles produces contraction while the other allows relaxation. Flexion (bending) occurs when contraction causes two bones to bend toward one another, while extension (straightening out) occurs from contraction of muscles, resulting in an increase in fee between two bones. Such pairs of muscles are called antagonistic. Often antagonistic muscles are in groups, forexample, both the brachialis and the biceps muscles flex the arm at the elbow and antagonize the triceps, but only when the palm is facing upwards. In pairs or groups of antagonistic muscle, one is usually much stron ger than the other. The biceps, which flex the arm are larger and more tendinous than the triceps which extends it.F When the body is at rest, the some of the antagonistic skeletal muscles remain in a state of contraction, called muscle tone, which holds the body in rigid position. If the somebody becomes unconscious, or is asleep, muscle tone is lost as the muscles relax completely.Questions1. A first class lever has the ____________ in the middle.2. bounce an example of a first class lever ____________________________3. Draw a diagram of a first class lever4. A second class lever has the ______________ in the middle.5. Give an example of a second classlever_________________________________6. Draw a diagram of a second class leverBones as Levers 8M. Poarch 2002http//science-class.net7. A third class lever has the _______________ in the middle.8. Give an example of a third class lever ____________________________9. Draw a diagram of a third class lever10. For EACH of the three cl asses of levers, explain the advantage gainedby using this type of lever.____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________11. What type of lever do we find most often in the human body?___________________________________________________________12. Explain how a muscle exerts force____________________________________________________________________________________________________________________________________________________________________________________Bones as Levers 9M. Poarch 2002http//science-class.net13. Examine the following diagrams, write down next to each picture whichclass of lever the picture represents and explain whyLever in thebodyType of lever and whyBones as Levers 10M. Poarch 2002http//science-class.net14. Describ e each of the followinga. Advantage (mechanical advantage)b. Antagonisticc. Effortd. Extensione. Flexionf. Forceg. Force armh. Fulcrumi. Insertionj. pink. Leversl. Limbsm. Loadn. Muscle toneo. Resistancep. Tendonq. Weight arm15.Circle and label eachone example of eachclass of lever on theskeleton.Label the fulcrum,effort and load foreach class of lever.GLOSSARYCENTER OF GRAVITY The point in any solid where a undivided applied force could support it the point wherethe mount of the tendency is equally balanced. The center of gravity is also called thecenter of mass. (When a man on a ladder leans sideways so far that his center ofgravity is no longer over his feet, he begins to fall.)GRAVITATION (GRAVITY) The force, first described mathematically by Isaac Newton, whereby any twoobjects in the Universe are attracted toward each other. (Gravitation holds themoon in orbit around the earth, the planets in orbit around the sun, and the sun inthe Milky Way. It also accounts for the fall of objects released near the surface ofthe earth. Objects near the surface of the earth fall at a rate of 32 feet per second.)FREE exit In physics, the motion of a body being acted on only by gravity.FRICTION The force of one surface sliding, rubbing, or rolling against another. friction slows down the motionof objects, and can create heat. Friction can also stabilize motion.FULCRUM The fixed point about which the lever moves. The point at which zip fastener is transferred.INERTIA The tendency for objects at rest to remain at rest, and objects in uniform motion to continue inmotion in a straight line, unless acted on by an outside force.LEVER A rigid rod or bar to which a force may be applied to overcome a resistance. A lever (or acombination of levers) is a simple machine used to gain force, gain speed, or change directions.LEVERAGE To sustain power with levers. Understanding where the fulcrum is located allows us to positionourselves to gain our greatest leverage.MACHINE A dev ice (or system of devices) made of piteous parts that transmits, site or changes a force.Machines are often modeled on how the human body works.SCIENCE An organized body of information or HOW THINGS WORK dim-witted MACHINE Machines powered by human force (as opposed to batteries, electricity or burning fuel)LOADIn bio-mechanics, the body mass is referred to as load.If an object is picked up, the load go outbe that of the body plus the objectbeen picked up. The body weightplace a load on the bone and musclestructures. If no load is applied, thebody willing stand still (inertia).To move the body load, force needs tobe applied. A lighter body loadrequires less applied force to bemoved and a stronger body will beable to move the body load faster.The secret of success is for the body to become stronger without the body gaining weight.2.2. FORCE (MOTIVE FORCE)Force = Mass x Acceleration. Force is the strength of the muscle push or pull required to movethe body mass (load). As long as the force applied on the muscle is equal to the load of the body,the body will not move and will be in equilibrium (state of rest).The force applied by the muscles must be bigger than the body mass (load) for the body to move.Strengthening the muscles will change the body to apply a larger force on the bones.The more force muscles apply on the bones, the faster the movement of the limbs will be.The long starting time endure-up clearlydemonstrates how the body shift change in accordancewith the force applied. Thebody angle will change toaccommodate the forceapplied.The primordial factor is how much strength training can be applied on the musclein an attempt to develop force before an hurt will occur in the form of a tornmuscle or a broken bone.2.2.1. Static force is a force that does not produce motion (The setposition in the 100m start).2.2.2. Centrifugal force is the force pulling outwards during rotation (Thediscus pulling in the hand during rotation).2.2.3. Centripetal force is the force pulling inwards during rotation. (Theforce pulling in the shoulder while delivering a discus).2.2.4. Eccentric force is an off-centre force. The centre ofgravity in the human body is more or less situated atthe navel. Delivering a shot needs an eccentric force todeliver the shot, as the shot is held next to the shoulderwhile delivering the shot. Eccentric force requires moremuscle strength than force executed in line with thecentre of gravity. In the sketch it can be seen that theshot is not in line (above) with the centre of gravity. Thekey-factor is to reduce movement away from the centreof gravity by either bringing the source that requires theapplied force e.g. the shot, closer to the body to avoidmuscle injury.2.2.5. Internal forces will be the force that is applied by the muscles on the bones in the limbs.2.2.6. international forces will be the force acting outside the body such as the gravity of the earth andfriction between bodies such as the feet and the groun d.2.3. INERTIAInertia is the bodys resistance to change position (Newtons 1st law Law of inertia). If no force isapplied on the body, the body will not move.2.3.1. Moment of inertia = mass x radius squared. Moment of inertia, normally a very shortperiod of time, is the moment the body is standing still or in a state of rest e.g. in pole vault,the flying of the body will follow an upwards and downwardly motion. At the point whereupwards motion change to downwards motion, a moment of inertia will exist.2.4. WORKWork is force x distance in the direction of force e.g. the amount of time the push or pull of themuscles is required to move the body over a 1500m x the 1500m = work required.The key factor is to develop the expertness of the body to operate at a work rate of e.g. 110% duringtraining. The athlete will then be able to operate at 91% (100% 110%) during competition toachieve success, with less injury risk to the body.If an 800m athlete wants to electioneering 60 seconds per 400m lap in competition, the training repetitionsshould be at 54.6 seconds. Training at repletion times of 54.6 seconds will enable the athlete run at91% capacity and run a time of 60 seconds in per 400m lap.Mechanical work = product of weight lifted x distance lifted2.5. GRAVITYGravity is a force that is always present. It is the magnetic force of the earth which pulls objectsvertically downwards to the centre of the earth.2.5.1. Centre of gravity is the pointin a body where force actsthrough. A solid body likethe shot or discus will havea fixed centre of gravity butin the human body thecentre of gravity will bedetermined by the positionof the body.2.6. TORQUETorque is the force causing an object to rotate x length of lever arm e.g. a longer arm requires moreforce to deliver a javelin than a shorter arm. divulge factor If competent force can be exerted on a longer arm, the longer arm is likely to generatemore torque e.g. a longer arm will throw a javelin further than a short arm because more torque canbe applied on the javelin during the process of delivery.2.6.1. External unbalanced torque must be applied to create angular velocity.Newtons 1st law A body will remain at rest, ormotion will be in a uniform straight line, until anexternal force is applied to change its direction isrelevant.To deliver a javelin, an upward and forwardmovement of the arm is required. The arm holding thejavelin will have to exceed the force required to movethe javelin forward as well as to overcome thedownward force of gravity, before a javelin will beable to travel in a temporary upwards trajectory after(prenominal)delivery.2.7. AXISAn axis is a straight line about which a body rotates.2.7.1. Vertical axis of the body passes throughbody from top to prat when standing inthe upright position.2.7.2. Sagittal (also called anteroposterior) axis ofthe body is an axis parallel to the groundwhich passes through the body from frontto back. Key factor The sprinter will movefrom start to finish as fast as possiblewithout changing the distance of thesagittal axis from the ground (Moving upand down).2.7.3. Frontal axis of the body is the axis parallelto the ground passing through the bodyfrom side to side e.g. the shortest distancebetween 2 points is a straight line. Keyfactor The sprinter will move from start tofinish as fast as possible without changingthe distance of the frontal axis from thesagittal axis (Moving side to side).2.7.4. Horizontal (also called transverse) axis is an axis which is parallel to the ground and can besagittal or frontal.The sketches below show how the 3 axiss is applied in bio-mechanics2.8. ACCELERATIONWhen the body is moving, the speed that it is moving, and the time ittakes to move from one point to the next point defines acceleration.Acceleration is the rate of change of velocity.Acceleration of the body is in proportion with the force applied bythe muscles in the body. More force will ensure greater acceleration.2.8.1. Angular acc eleration is the rate of change of angular velocity e.g the angular acceleration ofa high jumper crossing the cross bar.2.8.2. Positive acceleration means the velocity increases faster and faster e.g. a sprinter running gamethe 1st 100m of a 400m sprint.2.8.3. Negative acceleration is velocity decelerating (slowing down) e.g. a sprinter running the last100m of a 400m sprint and exhaustion is resulting in a bring down muscle force.2.8.4. An object free falling downwards accelerates at 9.8m/sec. e.g. to deliver a javelin, the forceapplied must be more than the body mass, the mass of the javelin and gravity force.After delivery of the javelin in an upwards direction, gravity will continuously pull the javelinback to earth at a rate of 9.8m/sec. The point of return will be when the combined force ofthe body the javelin and gravity are reduced to a force less than the force of gravity(9.8m/sec).The trajectory of the javelin will consist of positive acceleration (going up), a moment ofin ertia (changing direction) and negative acceleration (going down).Key factor The bigger the eccentric force applied during the delivery of the javelin, thelonger negative acceleration will be delayed. (The javelin will travel further before returningto the ground).2.9. SPEEDSpeed is the rate of change of a position. For a sprinter speed will mean the stride length x stridefrequency. For a jumper speed will mean the speed during take-off. For a thrower the speed willmean the speed during delivery of the implement.2.10. VELOCITYOnce the force applied on the body (muscle contraction), is bigger than the load (body mass), thebody will start moving (positive acceleration). The speed per second that the body change positionin a given direction = velocity. If a sprinter covers 100m in 10 seconds the velocity of the athlete willbe 100 10 = 10m/s.2.10.1. Optimal velocity is sometimes called maximum velocity2.10.2. Angular velocity is the angle through which the body turns per second e.g. d uring the periodof time that the jumper travels through air after take off.2.11. MOTIONMotion is the continuous change of position. As long as force is applied, motion will take place e.g.as long as the athlete is running motion takes place.2.11.1. Linear motion is movement in a straight line from one point to another e.g. a sprinter fromstart to finish.2.11.2. Rotational motion is movement around an axis of rotation e.g. the arms and legs of asprinter is moving in note movements while moving forward.2.11.3. General motion is a combination of linear motion and rotational motion e.g. In the 100m, thebody of the sprinter is moving forward in a straight line but the arms and legs is moving in acircular motion. In discus the thrower moves from the back of the circle to the front of thecircle while the body is turning around in circles in an attempt to gain maximum speed of thediscus prior to delivery.2.11.4. Uniform motion is steady, constant motion with unchanged speed e.g a 10000m at hlete willtry to run economically in an attempt to maintain the pace of running (uniform motion) aslong as possible.2.12. MOMENTUMMomentum is the quantity of motion of a moving body. Momentum = mass x velocity2.12.1. Angular momentum is the moment of inertia x angular velocity2.13. FRICTIONThe level of smoothness of two surfaces making contact will determine the level of friction. Thesmoother the surfaces, the more likely a gliding (slip) motion will appear when force is applied at anangle.A sprinter has to accelerate as fast as possible. To do this force has to be applied through the feetonto the ground in a running action to ensure forward movement. Fast acceleration may cause thefeet to slip on the ground. To avoid slipping the friction between the feet and ground is increased.This is do by wearing spikes in the running shoes to create as much friction as possible betweenthe surfaces of the track and the running shoes.2.14. balance wheelEquilibrium is another word for balance. When the resultant of all forces acting on a body are zero(neutralizing each other), the body is in equilibrium.A body at rest is in equilibrium. The sprinter in the set position is inequilibrium. When you lie still on a bed, the body is in equilibrium. Theforce of the body pressing against the bed and the force of the bedpushing back are equal, resulting in the body lying still. (Newtons 3rdlaw Law of answer For every action there is an equal and oppositereaction).2.15. ENERGYEnergy is the capacity to do work. There are 2 types of energy2.15.1. Potential energy When the body is standing still (equilibrium) no energy is used, but thepotential for it to move is always there.2.15.2. Kinetic energy is created when the forces applied on the body causes the body to move.The force applied to stop the body will equal the energy used to move. The more force isapplied, the faster the body will move and the more kinetic energy the body will have.Injuries occur when kinetic energy is transf erred to potential energy to quickly e.g. when the bodycome to a standstill overdue to external forces such as in a car accident, or the pull on the muscle is tobig for the muscle to handle and the muscle will tear. It is important that once kinetic energy iscreated and the result is a fast moving object, the slowing down process must be within the capacityof the muscles that causes the decelerati