PowerPoint Chapter 8 Flashcards
What is a machine?
Machine: an apparatus or system that uses the combined action of several parts in order to apply mechanical force
The human body uses ____ to accomplish tasks?
The human body uses machines to accomplish tasks
The human body is composed of ____?
The human body is composed of machines
The human body fits the definition of a ____ and is therefore a ____ itself?
The human body fits the definition of a machine and is therefore a machine itself
Any given joint in the musculoskeletal system can technically be classified as an ____ ____?
Any given joint in the musculoskeletal system can technically be classified as an intrinsic machine
What are the types of machines used in the human body?
Lever systems
Wheel-and-axle systems
Pulley systems
What are the four functions machines can fulfill?
Transmit a force
(Tendons transmit muscle forces to bones)
Increase the magnitude of a force
(Less effort required to move a given resistance)
Increase the linear distance and velocity of a force
Change the direction of a force
What structure in the body transmits forces from muscles?
Tendons
What is a lever system?
A lever System consists of a rigid or semi-rigid object (Lever) that is capable of rotating about an axis called a fulcrum
What are the three parts of a lever?
Rigid lever - Bone
Fulcrum – Joint
Eccentrically applied force - Muscle
The fulcrum is an an ____ ____ ____?
The fulcrum is an axis of rotation
The force in a lever system must be off-axis to produce ____?
torque
Levers transmit ____ from one place to another?
Levers transmit energy from one place to another
What is motive torque?
Motive Torque
Force applied to attempt to move the lever in one direction
What is resistive torque?
Resistive Torque
Force resisting the rotation of the lever in the opposite direction
What is the force applied to attempt to move the lever in one direction called?
Motive torque
What is the force resisting the rotation of the lever in the opposite direction called?
Resistive torque
What is mechanical advantage?
Mechanical Advantage
Relationship of motive force to a given resistive force
The amount of 1 required to overcome the other.
Location of ____ is the key to Mechanical Advantage?
Fulcrum
What are the three general locations the fulcrum can be and what is the advantage of each?
(Location of Fulcrum is the key to Mechanical Advantage)
Middle – no clear advantage
Far away – Adv. Motive force
Closer – Adv. Resistive force
How are levers classified?
Lever systems are classified according to the positions of the fulcrum, the motive force, and the resistive force.
What are the three types of lever and their orientation?
First-class lever systems (Motive force–fulcrum–resistive force)
Second-class lever systems (fulcrum–resistive force–motive force)
Third-class lever systems (Fulcrum–motive force–resistive force)
Which type of lever is the most versatile?
First-class levers
Four examples of a first-class lever?
Best Example 1st class levers
Teeter-totter –Balanced forces
Cutting tools – scissors
Shovel
Prying tools like a crow bar – adjustable fulcrum
What are first-class levers in the human body?
Triceps extension
Cervical extension
Plantarflexion
In second-class levers the moment arm of the ____ force will always be greater than the moment arm of the ____ force?
In second-class levers the moment arm of the motive force will always be greater than the moment arm of the resistance force
What are second-class levers always used for?
Always used to gain advantage in force production
What are 4 limitations to second-class levers?
Not as versatile as 1st class lever
No real gains in linear ROM
Lever cannot balance 2 forces
Lever cannot change direction of moving resistance.
What are two examples of second class levers in the body?
Push up
Front Arm Raise (eccentric)
In third-class levers the moment arm for ____ force is always less than moment arm of ____ force?
In third-class levers the moment arm for motive force is always less than moment arm of resistive force
What is gained in third-class lever systems?
Advantages gained in linear ROM and velocity
What does a short motive moment arm mean for force?
Short moment arm means no advantage in force production. Extra large forces needed.
What type of lever is most represented in the body?
Third-class levers
What are 4 examples of third-class levers?
Shovel
Broom
Tweezers or tongs
Rod and reel
What are three examples of third-class levers in the human body?
Hamstrings
Deltoid
Biceps curl
What does a pulley system consist of?
Consists of an object that acts as a wheel around which a flexible cord or cable is pulled
What are pulley systems used for in the human body?
In the human body, pulley systems are used to:
-Change the effective direction of the applied force
-Transmit forces
-Gain an advantage in force by changing the angle of pull for the muscle
What is the angle of pull+3 examples?
Angle at which the muscle force acts relative to a given axis or lever
Examples in the body:
-Quad muscles and patella
-Gracillis and medial condyle
-Peroneus Longus and lateral malleolus
What does a wheel and axle system consist of?
Consists of an object acting as a wheel that is secured to a smaller wheel or shaft called the axle
Examples of wheel and axle system?
Steering wheel, Screw Driver, Faucet, Door knob
A wheel an axle system is actually a lever system with________________________________?
Actually a lever system with tangential force applied to a moment arm equal to the radius of the wheel or axle
What can wheel and axle arrangements do?
Wheel-and-axle arrangements can:
-Transmit a force
-Gain an advantage in force or linear range of motion and velocity depending upon whether the force is applied to the wheel or the axle
Describe the wheel and axle system?
Wheel-and-axle arrangements can:
Transmit a force
Gain an advantage in force or linear range of motion and velocity depending upon whether the force is applied to the wheel or the axle
When the force is ____, torque is produced?
When the force is eccentric, torque is produced.
Explain how a larger wheel applies more force?
-The larger the wheel, the more off-axis the force is applied (greater radius of rotation).
-Therefore, a large wheel provides a large moment arm for the applied force.
What are three examples of a wheel and axle system in the human body?
Skull/Head
Trunk/Spine
Internal and external rotators
Much of human movement is a result of ____ ____ ____— designed for velocity over force production?
Much of human movement is a result of class-three levers— designed for velocity over force production
Longer levers allow ____ ____ at the distal ends of limbs?
Longer levers allow higher velocity at the distal ends of limbs
Longer arms have the potential to throw ____ and longer legs have the potential to run ____?
Longer arms have the potential to throw faster and longer legs have the potential to run faster
Humans have developed tools that essentially increase the ____ ____ ____ and therefore the ultimate ____ possible?
Humans have developed tools that essentially increase the length of limbs and therefore the ultimate velocity possible
(Rackets, bats, clubs, and lacrosse and hockey sticks)
Lighter weight materials allow implements to grow ____ with no effect on ____ them?
Lighter weight materials allow implements to grow longer with no effect on accelerating them.
(Aluminum bats vs wood bats)
What are two types of adapted motion?
Wheelchair racing
-Manual: (hands propel the chair by applying force directly through the wheels
Different rings on the wheels allow racers to apply force through different moment arms.)
-Handcycle: (chair is propelled via a chain and sprockets similar to a racing bicycle
The moment arm remains the same, and mechanical advantage is derived from multiple gears.)
