Physics of Centre of Gravity and Levers

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Questions and Answers

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?

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?

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?

Upper legs Signup and view all the answers

What is the computed mass of the torso and head segment for a person weighing 70 kg?

41.5 kg Signup and view all the answers

What is the primary factor that affects force development in muscles?

The length of the muscle when stimulated Signup and view all the answers

In pennate muscles, what is the impact of physiological cross-sectional area (PCSA) compared to parallel muscles?

It is larger, resulting in increased force production Signup and view all the answers

Which component of a lever is referred to as the point where the load is pivoted?

Fulcrum Signup and view all the answers

What determines the moment of a force in a lever system?

The magnitude of the force and the distance from the axis of rotation Signup and view all the answers

How does a lever function as a simple machine?

It can magnify the effort applied to lift or balance a load Signup and view all the answers

What is the term used to describe the rotational force that allows an object to rotate about its axis?

Torque Signup and view all the answers

Which statement is true about muscle length and force production?

Optimal force is generated at the muscle's resting length Signup and view all the answers

What describes the load in a lever system?

The resistance the lever is trying to overcome Signup and view all the answers

What is the significance of the centre of gravity in biomechanical calculations?

It affects the stability of an object. Signup and view all the answers

For uniformly dense and symmetric objects, where is the centre of gravity typically located?

At the geometric centre. Signup and view all the answers

Which factor does NOT determine the maximum tension achievable by human muscle?

The temperature of the environment. Signup and view all the answers

What is required for an object to achieve static equilibrium?

The sum of all forces must equal zero. Signup and view all the answers

What defines a mechanical advantage in the context of levers?

The ability to lift heavier weights with less effort. Signup and view all the answers

Which class of lever is represented when the load is located between the effort and the fulcrum?

Class II Lever Signup and view all the answers

What is a common risk associated with poor lifting techniques?

Improper alignment of the centre of gravity. Signup and view all the answers

How is torque defined in the context of biomechanics?

The product of force and distance from the pivot point. Signup and view all the answers

What condition is required for the leg to remain stationary when the hamstring muscle contracts?

Net Torque must equal zero Signup and view all the answers

What does a mechanical advantage (M.A.) greater than 1 indicate?

The applied force is less than the load force Signup and view all the answers

In a Class III lever system, where is the applied force generated in relation to the load force?

Between the fulcrum and load force Signup and view all the answers

What typically happens to the stress on lumbar vertebrae when a person lifts heavy objects?

Stress increases significantly Signup and view all the answers

Which of the following best describes a Class III lever system?

Designed for speed and range of motion Signup and view all the answers

Which statement is true about the mechanical advantage of the calf muscles during standing?

M.A. is greater than 1 and indicates efficiency Signup and view all the answers

What injury risk increases when using poor lifting techniques?

Back injury due to excessive force generation Signup and view all the answers

What force needs to be calculated alongside the force in the biceps muscle when holding a weight in equilibrium?

Force at the elbow joint Signup and view all the answers

What is the formula to calculate torque in the context of the skeletal lever system?

τ = F * sin θ * d Signup and view all the answers

If a force of 445 N acts at an angle of 82°, how much of that force acts perpendicular to the distance?

440.7 N Signup and view all the answers

Which moment direction does the force generated by F1 cause given it acts at a distance d1?

Anticlockwise Signup and view all the answers

In the calculation of torque, what role does angle θ play?

It affects the component of force acting perpendicular to the distance. Signup and view all the answers

What happens to the lower leg as a result of the clockwise torque produced about the knee?

It rotates in a clockwise direction. Signup and view all the answers

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?

2.89 Nm Signup and view all the answers

What describes the relationship between the force and distance in the skeletal lever system?

The torque depends on both the force magnitudes and their distances from the pivot. Signup and view all the answers

Why is it essential to consider the angle when calculating torque in the human body?

Forces don't align with distances in most cases. Signup and view all the answers

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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Description

Explore the principles of centre of gravity, stability, and lever mechanics in this quiz. Understand how forces and muscle dynamics influence movement and stability. Test your knowledge on these fundamental concepts in physics.