Biomechanics and Kinesiology

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Questions and Answers

What is the Center of Gravity (COG) also referred to as?

Point of Application

Equilibrium Point

Centre of Mass (correct)

Gravity Vector

What is the definition of gravity?

A force that acts in opposition to weight.

A type of motion experienced by objects.

The pull of the Earth on a body or its segments. (correct)

An external force that only affects living creatures.

Which statement accurately describes the direction of the gravitational force?

It varies in direction based on location.

It acts upwards away from the Earth.

It acts tangentially to the surface of the Earth.

It is directed towards the center of the Earth. (correct)

Which equation represents the magnitude of gravitational force?

Fg = gm1m2/r² Signup and view all the answers

What does Segmental COG refer to?

The center of gravity of a specific body segment. Signup and view all the answers

Which of the following is NOT a characteristic of gravity as described?

Gravity can change direction based on the object's mass. Signup and view all the answers

Which of the following best explains the concept of equilibrium in relation to gravity?

The balance of forces acting on an object. Signup and view all the answers

What does the line of application of gravity refer to?

The centre of mass of the object. Signup and view all the answers

Where is the center of gravity (COG) located in a symmetrical object?

At the geometric center of the object Signup and view all the answers

What happens to the location of the COG when the trunk is inclined forward?

It moves outside the body Signup and view all the answers

Which factor does NOT contribute to the stability of an object?

Size of the object's color Signup and view all the answers

What is stable equilibrium characterized by?

The body is displaced and returns to its original position Signup and view all the answers

How is the line of gravity (LOG) best visualized?

As a straight line connecting the COG to the ground Signup and view all the answers

When can a body be in neutral equilibrium?

When it remains in its position without changing height Signup and view all the answers

What does an increase in the base of support (BOS) generally signify?

Greater stability of the object Signup and view all the answers

What is the primary role of segments in the human body regarding COG?

Each segment can be represented by its own COG Signup and view all the answers

Which of the following contributes to unstable equilibrium?

Initial displacement increases Signup and view all the answers

What effect does heavier weight have on stability?

It increases stability Signup and view all the answers

What is the effect of a larger base of support (BOS) on the location of the line of gravity (LOG)?

The LOG has more freedom to move without falling. Signup and view all the answers

How does the height of the center of gravity (COG) affect an object's stability?

A higher COG decreases stability. Signup and view all the answers

What happens to the center of gravity (COG) when a person holds a heavy object in one hand?

The COG shifts up and to the right. Signup and view all the answers

How does the application of a cast to a limb impact the center of gravity (COG)?

The COG shifts down and to the right. Signup and view all the answers

What effect does relocating the COG have when external mass is added to the body?

It will shift toward the direction of the additional weight. Signup and view all the answers

What must occur for an object to maintain stability while standing on one leg?

The LOG must be centered within the BOS. Signup and view all the answers

When a person leans to one side while carrying a heavy object, what is the primary reason for this action?

To bring the line of gravity back to the middle of the base of support. Signup and view all the answers

Which arrangement supports greater stability for an individual?

Standing with legs spread apart. Signup and view all the answers

Study Notes

Gravity

Gravity is an external force with a consistent pull from the earth on objects, acting on the human body.
Defined as mutual attraction between the Earth and an object, directed towards the center of the Earth.
Gravitational force is a vector quantity with point of application at the Center of Gravity (COG).

Center of Gravity (COG)

COG is a hypothetical point where all mass of an object seems to be concentrated.
In symmetrical objects, COG is located at the geometric center; in asymmetrical objects, it shifts towards the heavier end.
Each body segment has its own COG, which can be combined into a single COG when segments are assessed collectively.

Line of Gravity (LOG)

The LOG is the vertical line of force due to gravity, always directed downwards toward the center of the Earth.
Visualization of LOG can be compared to a string with a weight, tied to the COG of an object.

Base of Support (BOS)

BOS refers to the area supporting a rigid body in contact with a surface.
Different positions (lying, standing) create varying sizes of BOS, influencing stability.
Walking aids can increase a patient's BOS for improved stability.

Equilibrium

Equilibrium is a state where a body is at rest or in constant motion, with no translatory or rotatory motion.
Stable equilibrium restores the body to its original position after displacement, while unstable equilibrium exacerbates displacement.

Rules of Equilibrium

Larger BOS increases stability; closer COG is to BOS enhances stability.
An object is stable only if its LOG is within its BOS.
Greater mass and friction between BOS and the supporting surface also contribute to stability.

Stability and COG

For an object to remain stable, the LOG must remain within the BOS.
A wider BOS allows more freedom for the LOG without losing stability.
A lower COG decreases the likelihood of falling.

Relocation of Center of Gravity

The COG shifts with changes in segment arrangement or mass distribution.
Adding external mass redistributes the COG toward the additional weight.
Applying a cast or holding a heavy object shifts the COG and influences stability by altering the BOS.

Practical Examples

When standing with legs spread apart, the wider BOS allows for greater trunk movement with maintained stability.
Leaning on another object effectively increases the BOS.
Holding a suitcase shifts the COG upwards and necessitates compensatory leaning to return the LOG to a stable position.

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Description

In this quiz, you will explore the concepts of gravity, segmental center of gravity (COG), and equilibrium as they relate to biomechanics and kinesiology. Test your understanding of these fundamental principles and how they apply to the human body in various positions. Prepare to delve into the rules of equilibrium and their importance in movement and stability.

Biomechanics and Kinesiology - Week 3: Gravity