Podcast
Questions and Answers
Which of the following is NOT a behavioral property of the musculotendinous unit?
Which of the following is NOT a behavioral property of the musculotendinous unit?
- Contractility (correct)
- Irritability
- Extensibility
- Elasticity
The series elastic component of a muscle contributes to its elasticity.
The series elastic component of a muscle contributes to its elasticity.
True (A)
What term describes the ability of a muscle to respond to a stimulus?
What term describes the ability of a muscle to respond to a stimulus?
Irritability
The human body contains approximately ______ muscles.
The human body contains approximately ______ muscles.
What percentage of total body weight in adults is made up of muscles?
What percentage of total body weight in adults is made up of muscles?
Every muscle in the human body operates independently and is not organized into functional pairs.
Every muscle in the human body operates independently and is not organized into functional pairs.
What is the functional unit of the neuromuscular system?
What is the functional unit of the neuromuscular system?
A motor unit consists of a single motor neuron and all the ______ it innervates.
A motor unit consists of a single motor neuron and all the ______ it innervates.
Which of the following best describes a motor unit?
Which of the following best describes a motor unit?
Slow twitch muscle fibers reach peak tension quicker than fast twitch fibers.
Slow twitch muscle fibers reach peak tension quicker than fast twitch fibers.
Which type of muscle fiber typically generates more peak tension – fast twitch or slow twitch?
Which type of muscle fiber typically generates more peak tension – fast twitch or slow twitch?
______ fibers reach peak tension and relax more quickly than slow twitch fibers.
______ fibers reach peak tension and relax more quickly than slow twitch fibers.
How are the fibers arranged relative to the longitudinal axis in muscles with parallel fiber arrangement?
How are the fibers arranged relative to the longitudinal axis in muscles with parallel fiber arrangement?
In pennate fiber arrangements, muscle fibers run parallel to the tendon within the muscle.
In pennate fiber arrangements, muscle fibers run parallel to the tendon within the muscle.
In what type of fiber arrangement do short fibers attach at an angle to one or more tendons?
In what type of fiber arrangement do short fibers attach at an angle to one or more tendons?
In ______ fibre arrangement, short fibres attach at an angle to one or more tendons within the muscle.
In ______ fibre arrangement, short fibres attach at an angle to one or more tendons within the muscle.
Which of the following is an advantage of fusiform muscle architecture?
Which of the following is an advantage of fusiform muscle architecture?
Fusiform muscles have a smaller potential for physiological cross-sectional area, resulting in less force development compared to pennate muscles.
Fusiform muscles have a smaller potential for physiological cross-sectional area, resulting in less force development compared to pennate muscles.
What is a disadvantage of fusiform muscle architecture related to force development?
What is a disadvantage of fusiform muscle architecture related to force development?
A disadvantage of fusiform muscles is their smaller potential for physiological ______ area, affecting force development.
A disadvantage of fusiform muscles is their smaller potential for physiological ______ area, affecting force development.
What is an advantage of pennated muscle architecture?
What is an advantage of pennated muscle architecture?
In pennated muscles, all the force developed by the muscle fibers is directly in line with the tendons.
In pennated muscles, all the force developed by the muscle fibers is directly in line with the tendons.
According to the module content, force in tendon can be calculated by what equation?
According to the module content, force in tendon can be calculated by what equation?
In pennated muscles, Force in tendon = Force in fibres x cos(angle of ______).
In pennated muscles, Force in tendon = Force in fibres x cos(angle of ______).
Which type of muscle contraction involves the muscle shortening while producing tension?
Which type of muscle contraction involves the muscle shortening while producing tension?
During an eccentric muscle contraction, the muscle length shortens while producing tension.
During an eccentric muscle contraction, the muscle length shortens while producing tension.
What type of muscle contraction involves no change in muscle length?
What type of muscle contraction involves no change in muscle length?
In an ______ muscle contraction, there is no change in muscle length.
In an ______ muscle contraction, there is no change in muscle length.
Which of the following is NOT a role typically assumed by muscles?
Which of the following is NOT a role typically assumed by muscles?
An agonist muscle must always shorten to produce movement.
An agonist muscle must always shorten to produce movement.
Muscular strength is defined as the ability of a given muscle group to generate what at a particular joint?
Muscular strength is defined as the ability of a given muscle group to generate what at a particular joint?
Muscular strength is solely determined by the amount of tension the muscles can generate.
Muscular strength is solely determined by the amount of tension the muscles can generate.
What two components is muscle force often split into when muscles don't intersect the bone at 90 degrees?
What two components is muscle force often split into when muscles don't intersect the bone at 90 degrees?
The component of muscle force that is perpendicular to the bone and causes torque around the joint is known as the ______ component.
The component of muscle force that is perpendicular to the bone and causes torque around the joint is known as the ______ component.
A muscle attaches to a bone 5 cm from the joint center and exerts 150 N of tension at a 60-degree angle. What is the rotary component of the force?
A muscle attaches to a bone 5 cm from the joint center and exerts 150 N of tension at a 60-degree angle. What is the rotary component of the force?
The muscle force-length relationship suggests that a muscle produces maximum force at its shortest length.
The muscle force-length relationship suggests that a muscle produces maximum force at its shortest length.
What happens to the ability to generate tension as the overlap between actin and myosin is reduced?
What happens to the ability to generate tension as the overlap between actin and myosin is reduced?
Beyond resting length, tension builds in ______ tissues such as cell membranes and tendons.
Beyond resting length, tension builds in ______ tissues such as cell membranes and tendons.
What is the relationship between active and passive tension to achieve total tension?
What is the relationship between active and passive tension to achieve total tension?
Active insufficiency occurs when a muscle is fully stretched and can no longer produce force effectively.
Active insufficiency occurs when a muscle is fully stretched and can no longer produce force effectively.
What is an example of active insufficiency?
What is an example of active insufficiency?
______ insufficiency is defined as the restriction of joint range of motion when muscles are fully stretched.
______ insufficiency is defined as the restriction of joint range of motion when muscles are fully stretched.
What happens to the force developed by a muscle as the velocity of concentric contraction increases?
What happens to the force developed by a muscle as the velocity of concentric contraction increases?
In isometric muscle actions, the rate of length change is greater than zero.
In isometric muscle actions, the rate of length change is greater than zero.
In eccentric muscle actions, how does the force developed change as the muscle lengthening velocity increases?
In eccentric muscle actions, how does the force developed change as the muscle lengthening velocity increases?
An eccentric contraction followed immediately by a concentric contraction describes the ______ cycle.
An eccentric contraction followed immediately by a concentric contraction describes the ______ cycle.
What is stored in elastic tissues, which is then released along with the force produced by the contractile component during concentric contraction?
What is stored in elastic tissues, which is then released along with the force produced by the contractile component during concentric contraction?
Muscle cross-sectional area has no impact on the tension-generating capability of the muscle tissue.
Muscle cross-sectional area has no impact on the tension-generating capability of the muscle tissue.
Name one factor affecting the tension-generating capability of muscle tissue.
Name one factor affecting the tension-generating capability of muscle tissue.
The distance between the muscle attachment to bone and the joint center impacts the ______ of the muscles crossing the joint.
The distance between the muscle attachment to bone and the joint center impacts the ______ of the muscles crossing the joint.
What is the name for the product of muscular force and the velocity of muscle shortening?
What is the name for the product of muscular force and the velocity of muscle shortening?
Muscular power is solely determined by the amount of force a muscle can produce, irrespective of the speed of contraction.
Muscular power is solely determined by the amount of force a muscle can produce, irrespective of the speed of contraction.
What does the rate of torque production at a joint represent?
What does the rate of torque production at a joint represent?
The total tension is the sum of ______ and passive tensions within a muscle.
The total tension is the sum of ______ and passive tensions within a muscle.
Match the following muscle actions to their descriptions:
Match the following muscle actions to their descriptions:
Which of the following scenarios would result in the highest torque, given a muscle force of 50N?
Which of the following scenarios would result in the highest torque, given a muscle force of 50N?
Torque is calculated by multiplying the moment arm by the angle of the muscle's attachment to the bone.
Torque is calculated by multiplying the moment arm by the angle of the muscle's attachment to the bone.
What is the formula for calculating torque ($T_m$)?
What is the formula for calculating torque ($T_m$)?
When a muscle is at its resting length, there is ______ overlap of actin-myosin.
When a muscle is at its resting length, there is ______ overlap of actin-myosin.
Match the concept to its definition:
Match the concept to its definition:
Which of Newton's Laws states that an object in motion stays in motion unless acted upon by an external force?
Which of Newton's Laws states that an object in motion stays in motion unless acted upon by an external force?
According to Newton's First Law, an object at rest will stay at rest only if there are no forces acting on it.
According to Newton's First Law, an object at rest will stay at rest only if there are no forces acting on it.
What term describes the resistance of an object to changes in its state of motion?
What term describes the resistance of an object to changes in its state of motion?
Newton's Second Law of Motion states that force is equal to mass multiplied by ________.
Newton's Second Law of Motion states that force is equal to mass multiplied by ________.
What is the relationship between the mass of an object and its acceleration, according to Newton's Second Law, when the force applied is constant?
What is the relationship between the mass of an object and its acceleration, according to Newton's Second Law, when the force applied is constant?
The direction of the force vector in Newton's Second Law is opposite to the direction of the acceleration vector.
The direction of the force vector in Newton's Second Law is opposite to the direction of the acceleration vector.
Provide the formula that mathematically represents Newton's Second Law of Motion.
Provide the formula that mathematically represents Newton's Second Law of Motion.
Newton's Third Law of Motion states that for every action, there is an equal and ________ reaction.
Newton's Third Law of Motion states that for every action, there is an equal and ________ reaction.
When you jump, you exert a force on the ground. According to Newton's Third Law, what is the reaction force?
When you jump, you exert a force on the ground. According to Newton's Third Law, what is the reaction force?
According to Newton's Third Law, action and reaction forces act on the same object.
According to Newton's Third Law, action and reaction forces act on the same object.
Explain how Newton's Third Law applies to the propulsion of a rocket.
Explain how Newton's Third Law applies to the propulsion of a rocket.
A high jumper with a body weight of 712 N exerts a force of 3 kN against the ground during takeoff. According to Newton's third law, what force does the ground exert on the high jumper?
A high jumper with a body weight of 712 N exerts a force of 3 kN against the ground during takeoff. According to Newton's third law, what force does the ground exert on the high jumper?
When standing, ground reaction forces act in the opposite direction to the forces applied by your foot on the ground.
When standing, ground reaction forces act in the opposite direction to the forces applied by your foot on the ground.
In a scenario where a box sits on a table, the weight of the box generates a ________ force by the table.
In a scenario where a box sits on a table, the weight of the box generates a ________ force by the table.
If a kicker applies a force to give a stationary 2.5 kg ball an acceleration of 40 m/s², how much force must be applied?
If a kicker applies a force to give a stationary 2.5 kg ball an acceleration of 40 m/s², how much force must be applied?
According to Newton's Second Law, if the applied force is reduced by 50 percent, what happens to the acceleration?
According to Newton's Second Law, if the applied force is reduced by 50 percent, what happens to the acceleration?
If the applied force on an object is increased, the object's velocity will always increase.
If the applied force on an object is increased, the object's velocity will always increase.
A ________ is a sketch that shows a defined system in isolation with all of the force vectors acting on the system.
A ________ is a sketch that shows a defined system in isolation with all of the force vectors acting on the system.
What is the purpose of a free body diagram?
What is the purpose of a free body diagram?
What does a free body diagram represent in the context of Newton's laws?
What does a free body diagram represent in the context of Newton's laws?
The line of action and point of application of forces are not necessary when creating a free body diagram.
The line of action and point of application of forces are not necessary when creating a free body diagram.
In a free body diagram, all forces and ________ vectors external to the system of interest are shown.
In a free body diagram, all forces and ________ vectors external to the system of interest are shown.
Match each of Newton's Laws to its correct description:
Match each of Newton's Laws to its correct description:
Is a bicyclist turning a corner at $15$ km/hr in a state of uniform motion?
Is a bicyclist turning a corner at $15$ km/hr in a state of uniform motion?
Inertia represents resistance to velocity.
Inertia represents resistance to velocity.
As an astronaut performs a spacewalk and lets go of their screwdriver, what happens to the screwdriver according to Newton's First Law?
As an astronaut performs a spacewalk and lets go of their screwdriver, what happens to the screwdriver according to Newton's First Law?
According to Newton's Second Law, if the mass of an object is doubled while the force applied remains constant, what happens to the acceleration?
According to Newton's Second Law, if the mass of an object is doubled while the force applied remains constant, what happens to the acceleration?
A heavier object has less inertia than a lighter one.
A heavier object has less inertia than a lighter one.
The force exerted by the table on a book sitting on it, which counters the book's weight, is called the ________ force.
The force exerted by the table on a book sitting on it, which counters the book's weight, is called the ________ force.
What is the net force acting on an object that is in equilibrium?
What is the net force acting on an object that is in equilibrium?
What is the primary purpose of a free body diagram?
What is the primary purpose of a free body diagram?
In a free body diagram, the weight force always points downwards from the center of gravity if applicable.
In a free body diagram, the weight force always points downwards from the center of gravity if applicable.
When developing a free body diagram, what is done after identifying the system of interest?
When developing a free body diagram, what is done after identifying the system of interest?
When replacing external contacts with appropriate forces, it's important to understand the mechanical actions of common forces in ______ movement.
When replacing external contacts with appropriate forces, it's important to understand the mechanical actions of common forces in ______ movement.
Match the following scenarios with the mechanical actions of common forces:
Match the following scenarios with the mechanical actions of common forces:
Which of the following best describes the action of 'rope-like structures' in the context of free body diagrams for human movement?
Which of the following best describes the action of 'rope-like structures' in the context of free body diagrams for human movement?
When showing rope-like forces in a free body diagram, it's better to include the upper arm instead of isolating a segment.
When showing rope-like forces in a free body diagram, it's better to include the upper arm instead of isolating a segment.
In representing contact with a rough surface in a free body diagram, the 'surface' is replaced by how many forces?
In representing contact with a rough surface in a free body diagram, the 'surface' is replaced by how many forces?
For contact with a smooth surface, the force is located over the whole surface but is considered acting at the ______ of pressure.
For contact with a smooth surface, the force is located over the whole surface but is considered acting at the ______ of pressure.
Match the type of surface contact with its corresponding force representation in a free body diagram:
Match the type of surface contact with its corresponding force representation in a free body diagram:
What mechanical action replaces the axle during a 'free rotation around an axle' scenario in human movement?
What mechanical action replaces the axle during a 'free rotation around an axle' scenario in human movement?
In a 'constrained rotation around an axle', the axle is replaced ONLY by a force acting at the center of rotation.
In a 'constrained rotation around an axle', the axle is replaced ONLY by a force acting at the center of rotation.
In the context of free body diagrams, what two components replace an axle in a 'constrained rotation around an axle' scenario?
In the context of free body diagrams, what two components replace an axle in a 'constrained rotation around an axle' scenario?
In a constrained rotation around an axle, the torque can be either ______ or counter-clockwise.
In a constrained rotation around an axle, the torque can be either ______ or counter-clockwise.
Match the following types of rotation around an axle with their descriptions:
Match the following types of rotation around an axle with their descriptions:
When drawing a free body diagram of the gymnast performing a handstand, what is the first step?
When drawing a free body diagram of the gymnast performing a handstand, what is the first step?
When drawing a free body diagram, adding the reference frame should be done before drawing the weight force.
When drawing a free body diagram, adding the reference frame should be done before drawing the weight force.
In the example of the gymnast, what external forces should be considered when the system of interest is the gymnast?
In the example of the gymnast, what external forces should be considered when the system of interest is the gymnast?
In the gymnast example, F_GRF normal is the ______ force.
In the gymnast example, F_GRF normal is the ______ force.
Match the force acting on the gymnast with its description:
Match the force acting on the gymnast with its description:
What types of forces are associated with movement through a fluid?
What types of forces are associated with movement through a fluid?
When analyzing forces associated with humans moving through water, lift is always positive.
When analyzing forces associated with humans moving through water, lift is always positive.
Besides air resistance and lift, which other force must be taken into account when waterskiing?
Besides air resistance and lift, which other force must be taken into account when waterskiing?
In the waterskier example, Step 1 of drawing a free body diagram is to isolate the ______ of interest.
In the waterskier example, Step 1 of drawing a free body diagram is to isolate the ______ of interest.
Match the free body diagram step with its action for the waterskier:
Match the free body diagram step with its action for the waterskier:
According to the steps for creating a free body diagram, after redrawing the system as a stick figure, what should be done next?
According to the steps for creating a free body diagram, after redrawing the system as a stick figure, what should be done next?
After adding force of gravity, show reference frame and friction.
After adding force of gravity, show reference frame and friction.
In analyzing human movement, what are the 5 steps of creating a free body diagram?
In analyzing human movement, what are the 5 steps of creating a free body diagram?
Common forces are important in ______ human movement.
Common forces are important in ______ human movement.
Match the following force types with their typical representation in a free body diagram:
Match the following force types with their typical representation in a free body diagram:
Flashcards
Extensibility
Extensibility
The ability of a muscle to be stretched or increase in length.
Elasticity
Elasticity
The ability of a muscle to return to its normal resting length after being stretched.
Irritability
Irritability
The ability of a muscle to respond to a stimulus.
Ability to develop tension
Ability to develop tension
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Amount of muscles in human body
Amount of muscles in human body
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Motor unit
Motor unit
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Fast Twitch (FT) Fibers
Fast Twitch (FT) Fibers
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Parallel (fusiform) fibre arrangement
Parallel (fusiform) fibre arrangement
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Pennate fibre arrangement
Pennate fibre arrangement
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Concentric contraction
Concentric contraction
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Eccentric contraction
Eccentric contraction
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Isometric contraction
Isometric contraction
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Agonist muscle
Agonist muscle
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Antagonist muscle
Antagonist muscle
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Stabilizer
Stabilizer
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Muscular strength
Muscular strength
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Muscular strength: Derived from
Muscular strength: Derived from
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Rotary component of muscle force
Rotary component of muscle force
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Stabilizing/Dislocating Component
Stabilizing/Dislocating Component
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Muscle force-length relationship
Muscle force-length relationship
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Active insufficiency
Active insufficiency
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Passive insufficiency
Passive insufficiency
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Concentric force-velocity relationship
Concentric force-velocity relationship
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Eccentric force-velocity relationship
Eccentric force-velocity relationship
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Stretch-shortening cycle
Stretch-shortening cycle
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Factors affecting tension-generating capability
Factors affecting tension-generating capability
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Muscular Power
Muscular Power
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Linear kinetics
Linear kinetics
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Newton's First Law (Law of Inertia)
Newton's First Law (Law of Inertia)
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Newton's Second Law (Law of Acceleration)
Newton's Second Law (Law of Acceleration)
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Newton's Third Law (Law of Reaction)
Newton's Third Law (Law of Reaction)
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Free Body Diagram (FBD)
Free Body Diagram (FBD)
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Purpose of FBDs
Purpose of FBDs
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Objectives of Free Body Diagrams
Objectives of Free Body Diagrams
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Free Body Diagram Definition
Free Body Diagram Definition
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Steps for Creating an FBD
Steps for Creating an FBD
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Rope-like Structure Forces
Rope-like Structure Forces
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Forces: 'Rough' Surfaces
Forces: 'Rough' Surfaces
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Forces: 'Smooth' Surfaces
Forces: 'Smooth' Surfaces
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Forces: Free Rotation (Axle)
Forces: Free Rotation (Axle)
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Forces: Constrained Rotation
Forces: Constrained Rotation
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Forces: Movement Through Fluid
Forces: Movement Through Fluid
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Study Notes
- Objectives include understanding how free body diagrams are used to construct a model of the forces acting on a body.
Purpose of a free body diagram
- A free body diagram is a pictorial representation of the left side of Newton's 2nd Law, expressed as ∑F = ma.
Developing a free body diagram
- There are five steps to creating a free body diagram:
- Identify the system of interest.
- Redraw the system as a stick figure.
- Draw the weight force pointing down from the center of gravity, if applicable.
- Replace all external contacts with appropriate forces.
- Show a reference frame.
Replacing External Contacts with Appropriate Forces
- Understanding mechanical actions of common forces in human movement is needed.
- Identify "possible" mechanical action forces that can exist between the system of interest and the outside world.
- Represents a framework for evaluating forces.
Mechanical actions of common forces in human movement
Rope-like Structures
- Examples include holding onto rings in gymnastics, tug of war, muscle/tendon complexes, and ligaments.
- The action of rope-like structures is a force pulls along the line of action of the structure.
- Muscle force can be shown as a force vector external to the isolated segment of interest.
Contact with a "Rough" Surface
- Examples include the ground reaction force and leaning against a wall.
- The "surface" (floor, wall, etc.) is replaced by two forces.
- One force is along the surface, created by friction.
- The other is perpendicular to the surface, called the normal force, which always pushes against the body.
- Forces are located over the whole surface, but are considered acting at the center of pressure.
Contact with a Smooth Surface
- An example is the ground reaction force when standing on ice.
- The "surface" (floor, wall, etc.) is replaced by one force perpendicular to the surface called the normal force, which pushes against the body.
- The force is located over the whole surface but considered acting at the center of pressure.
Free Rotation Around an Axle
- Free rotation around an axle refers to a pin joint free to move.
- An example includes bone-on-bone forces.
- The axle is replaced by a force in any direction, pushing or pulling, acting at the center of rotation.
Constrained Rotation Around an Axle
- Constrained rotation around an axle refers to a pin joint not free to move.
- An example included grasping a tool with an offset center of gravity
- Joint reaction forces are considered to act as a moment when muscles are considered.
- The axle is replaced by both a force and a torque.
- A force in any direction, pushing or pulling, acts at the center of rotation.
- A torque can be either clockwise or counter-clockwise.
Example: Gymnast
- The first step is to identify the system of interest.
- The person is the system of interest and one is interested in determining ground reaction forces.
- The second step is to redraw the system as a stick figure.
- The third step is to draw the weight force, or force of gravity if applicable.
- The fourth step is to replace all external contacts with appropriate forces.
- Horizontal force is associated with friction.
- Vertical force is called the "normal force" because it is perpendicular to the ground.
- The fifth step is to add a reference frame.
Fluid Movement
- Examples include air resistance (drag, lift) and water (biomechanics of swimming).
- The direction is dependent on the relationship between the velocity of flow and the velocity of the system and specific to the force in question.
Waterskiing example
- The first step is to isolate system of interest.
- The second step is to redraw system as stick figure.
- The third step is to add force of gravity.
- The fourth step is to replace all external contacts with appropriate forces like rope force, air force, lift and drag forces.
- The fifth step is to show the reference frame.
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