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Questions and Answers
What percentage of the total body mass does the upper arms segment represent?
What percentage of the total body mass does the upper arms segment represent?
- 0.053 x 50 kg
- 0.053 x M (correct)
- 0.053 x 70 kg
- 0.053 x 100 kg
To be stable, where must an object's centre of gravity be located in relation to its base of support?
To be stable, where must an object's centre of gravity be located in relation to its base of support?
- At the edge of the base of support
- Below the base of support
- Anywhere in relation to the base of support
- Above the base of support (correct)
If the total mass of a human body is 70 kg, what is the mass of the lower legs segment?
If the total mass of a human body is 70 kg, what is the mass of the lower legs segment?
- 11.8 kg
- 41.5 kg
- 8.4 kg (correct)
- 15.2 kg
Which segment of the body has the largest mass relative to a total body mass of 70 kg?
Which segment of the body has the largest mass relative to a total body mass of 70 kg?
What is the computed mass of the torso and head segment for a person weighing 70 kg?
What is the computed mass of the torso and head segment for a person weighing 70 kg?
What is the primary factor that affects force development in muscles?
What is the primary factor that affects force development in muscles?
In pennate muscles, what is the impact of physiological cross-sectional area (PCSA) compared to parallel muscles?
In pennate muscles, what is the impact of physiological cross-sectional area (PCSA) compared to parallel muscles?
Which component of a lever is referred to as the point where the load is pivoted?
Which component of a lever is referred to as the point where the load is pivoted?
What determines the moment of a force in a lever system?
What determines the moment of a force in a lever system?
How does a lever function as a simple machine?
How does a lever function as a simple machine?
What is the term used to describe the rotational force that allows an object to rotate about its axis?
What is the term used to describe the rotational force that allows an object to rotate about its axis?
Which statement is true about muscle length and force production?
Which statement is true about muscle length and force production?
What describes the load in a lever system?
What describes the load in a lever system?
What is the significance of the centre of gravity in biomechanical calculations?
What is the significance of the centre of gravity in biomechanical calculations?
For uniformly dense and symmetric objects, where is the centre of gravity typically located?
For uniformly dense and symmetric objects, where is the centre of gravity typically located?
Which factor does NOT determine the maximum tension achievable by human muscle?
Which factor does NOT determine the maximum tension achievable by human muscle?
What is required for an object to achieve static equilibrium?
What is required for an object to achieve static equilibrium?
What defines a mechanical advantage in the context of levers?
What defines a mechanical advantage in the context of levers?
Which class of lever is represented when the load is located between the effort and the fulcrum?
Which class of lever is represented when the load is located between the effort and the fulcrum?
What is a common risk associated with poor lifting techniques?
What is a common risk associated with poor lifting techniques?
How is torque defined in the context of biomechanics?
How is torque defined in the context of biomechanics?
What condition is required for the leg to remain stationary when the hamstring muscle contracts?
What condition is required for the leg to remain stationary when the hamstring muscle contracts?
What does a mechanical advantage (M.A.) greater than 1 indicate?
What does a mechanical advantage (M.A.) greater than 1 indicate?
In a Class III lever system, where is the applied force generated in relation to the load force?
In a Class III lever system, where is the applied force generated in relation to the load force?
What typically happens to the stress on lumbar vertebrae when a person lifts heavy objects?
What typically happens to the stress on lumbar vertebrae when a person lifts heavy objects?
Which of the following best describes a Class III lever system?
Which of the following best describes a Class III lever system?
Which statement is true about the mechanical advantage of the calf muscles during standing?
Which statement is true about the mechanical advantage of the calf muscles during standing?
What injury risk increases when using poor lifting techniques?
What injury risk increases when using poor lifting techniques?
What force needs to be calculated alongside the force in the biceps muscle when holding a weight in equilibrium?
What force needs to be calculated alongside the force in the biceps muscle when holding a weight in equilibrium?
What is the formula to calculate torque in the context of the skeletal lever system?
What is the formula to calculate torque in the context of the skeletal lever system?
If a force of 445 N acts at an angle of 82°, how much of that force acts perpendicular to the distance?
If a force of 445 N acts at an angle of 82°, how much of that force acts perpendicular to the distance?
Which moment direction does the force generated by F1 cause given it acts at a distance d1?
Which moment direction does the force generated by F1 cause given it acts at a distance d1?
In the calculation of torque, what role does angle θ play?
In the calculation of torque, what role does angle θ play?
What happens to the lower leg as a result of the clockwise torque produced about the knee?
What happens to the lower leg as a result of the clockwise torque produced about the knee?
If a deltoid muscle exerts a force of 67 N at an angle of 15° and the force-application point is 18 cm from the shoulder joint, what would be the torque caused by the deltoid?
If a deltoid muscle exerts a force of 67 N at an angle of 15° and the force-application point is 18 cm from the shoulder joint, what would be the torque caused by the deltoid?
What describes the relationship between the force and distance in the skeletal lever system?
What describes the relationship between the force and distance in the skeletal lever system?
Why is it essential to consider the angle when calculating torque in the human body?
Why is it essential to consider the angle when calculating torque in the human body?
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Study Notes
Centre of Gravity
- The centre of gravity (CofG) is the point where an object's weight is evenly distributed.
- The CofG is the point where the force of gravity acts.
- The CofG of a uniformly dense and symmetric object is located at its geometric centre.
Centre of Gravity and Stability
- An object is stable when its centre of gravity lies above its base of support.
- The base of support is the area of contact between an object and the supporting surface.
Force Development
- The force (tension) a muscle can produce depends on its cross-sectional area (CSA) and length at the time of stimulation.
- Maximum tension is achieved when the muscle is stimulated at its normal resting length.
Levers
- A lever is a rigid rod that rotates around a fixed point called a fulcrum.
- Muscles provide the force to move the lever.
- The moment of a force is the turning effect of the force on an object.
- The moment of a force is calculated by multiplying the force by the distance from the axis of rotation.
- Torque is the rotational force that causes an object to rotate around its axis.
Moment of a Force
- The magnitude of the torque generated is the product of the force and the perpendicular distance from the line of action of the force to the pivot.
- To calculate torque, use the formula: τ= 𝐹𝑠𝑖𝑛 𝜃 𝑑
- The angle θ is measured between the force and the distance.
Equilibrium
- An object is in equilibrium when the net force and net torque acting on it are zero.
- Equilibrium can be achieved by balancing clockwise and anticlockwise torques.
Mechanical Advantage
- Mechanical advantage (MA) is the ratio of the load force to the applied force.
- MA indicates whether a larger applied force is needed than the load force.
- MA is calculated by dividing the load force (Fl) by the applied force (Fa): 𝑀𝐴 = 𝐹𝑙/ 𝐹𝑎
- Class I levers have the fulcrum between the effort and the load, MA > 1, designed for strength.
- Class II levers have the load between the fulcrum and the effort, MA > 1, designed for strength.
- Class III levers have the effort between the fulcrum and the load, MA < 1, designed for speed and range of motion.
Back Injury
- Increased stress on the lumbar vertebrae can lead to injury.
- Poor lifting technique can result in back injury due to the requirement to generate large forces in the back muscles.
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