Physics Chapter: Gravitational Force & COG

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Questions and Answers

What is the direction of the gravitational force acting on an object?

Perpendicular to the ground

Towards the center of the earth (correct)

At an angle to the object

Away from the center of the earth

In a symmetrical object, where is the Center of Gravity (COG) located?

Randomly distributed throughout

Towards the heavier end

At the base of the object

At the geometric center (correct)

What is the Line of Gravity (LOG) visualized as?

A string with a weight at the end attached to the COG (correct)

A reference line parallel to the ground

A line drawn at a right angle to the surface

An invisible line extending from the center of mass

When an object is inclined forward, where does its Center of Gravity typically lie?

Outside the body Signup and view all the answers

Which statement about Base of Support (BOS) is correct?

BOS can expand with the use of mobility aids. Signup and view all the answers

Which statement is true regarding the Line of Gravity?

It extends vertically from the center of gravity to the ground Signup and view all the answers

What happens when the line of gravity (LOG) falls outside the base of support (BOS)?

The object will fall. Signup and view all the answers

What defines the Center of Gravity (COG) in an asymmetrical object?

It is located towards the heavier end of the object Signup and view all the answers

What is true regarding static equilibrium?

It involves bodies at rest. Signup and view all the answers

How does a larger base of support affect stability?

It allows more freedom for the line of gravity (LOG). Signup and view all the answers

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

The color of the object Signup and view all the answers

Which of the following conditions does NOT enhance stability?

A slick supporting surface Signup and view all the answers

What effect does lowering the center of gravity (COG) have on an object's stability?

It increases stability. Signup and view all the answers

What is the result of adding external mass to the body?

The COG shifts towards the added weight. Signup and view all the answers

How does using crutches affect stability when standing on one leg?

It enlarges the base of support (BOS). Signup and view all the answers

What occurs in the toe region of tissue response to loading?

The tissue experiences elastic deformation. Signup and view all the answers

What is the primary aim of rehabilitation in relation to tissue homeostasis?

To increase the envelope borders of loading thresholds. Signup and view all the answers

What effect does compression loading have on tissue?

It leads to increased pressure and facilitates fluid flow within the tissue. Signup and view all the answers

Why is tension loading used in rehabilitation?

To elongate shortened tissues and break excessive cross links. Signup and view all the answers

How does the adaptive ability of tissue change with injury?

It narrows, requiring precise dosage of loading to maintain function. Signup and view all the answers

What is the relationship between torque and the moment arm in a muscle contraction?

Torque is a product of the magnitude of applied force and the moment arm. Signup and view all the answers

What occurs to the center of gravity (COG) when the line of gravity (LOG) shifts toward the right foot?

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

What angle is the moment arm typically equal to during muscle force application?

90 degrees Signup and view all the answers

How does the moment arm of gravity change as body segments move in space?

It changes as the angle of application of gravity alters. Signup and view all the answers

What happens to the moment arm of a muscle force when the applied action line is at 90 degrees?

The moment arm is maximized. Signup and view all the answers

What is a lever arm (LA)?

It is the distance from the axis to the point of force application. Signup and view all the answers

Why does the man lean to the left when the line of gravity moves to the right?

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

When does gravity exert its maximum torque on a body lever?

When the segment is parallel to the ground. Signup and view all the answers

Study Notes

Gravitational Force

Mutual attraction between the earth and an object
Directed towards the center of the earth
Vector quantity
Point of application: COG
Line of application: Center of mass of object
Direction: Towards center of the earth
Magnitude: Equal to gravitational force

Center of Gravity (COG)

Hypothetical point where all mass appears concentrated
Point where the force of gravity appears to act
Located at the geometric center of symmetrical objects
COG shifts towards the heavier end in asymmetrical objects

COG in the Human Body

Each segment of the body has its own COG
When segments are combined, a single COG can be used to represent the gravity acting on them
Location of COG changes with posture variations

Line of Gravity (LOG)

Imaginary vertical line from the COG to the ground
Represents the direction gravity acts on an object or person
Can be visualized as a plumb line attached to the COG

Positions and COG

With good posture, the LOG passes through the mid-cervical and mid-lumbar vertebrae, and in front of the thoracic vertebrae

Base of Support (BOS)

Area where an object is supported and in contact with the supporting surface
In lying position: Posterior aspect of the whole body forms the BOS
In stride standing: Area as wide as the feet and as long as the distance between their outer borders
Walking aids increase BOS for patients

Equilibrium

Static: State where bodies are at rest
Dynamic: State where bodies are moving at a constant velocity
Equilibrium occurs when forces acting on a body are perfectly balanced

Rule of Equilibrium

Larger BOS = greater stability
Closer COG to BOS = more stability
LOG must fall within BOS for stability
Greater mass = greater stability
Greater friction between supporting surface and BOS = greater stability

Stability and COG

For stability, LOG must fall within the BOS
When LOG falls outside the BOS, the object will fall.
Larger BOS allows greater freedom of movement for the LOG without losing stability

Relocation of the Center of Gravity

Depends on arrangement of segments in space and distribution of mass
Adding external mass shifts COG towards the additional weight

Torque

Force needed by a muscle contraction to cause rotatory joint motion
The product of the magnitude of applied force (F) and the distance (r) from the axis of rotation.
T= rFsin(θ)

Moment Arm

Length of a line perpendicular to the force vector and intersecting the joint axis.
The length is related to the angle of application of force.
Lever arm is the distance from the axis to the point where force is applied.

Moment Arm of a Muscle Force

Greatest when the action line is applied at 90 degrees to its lever arm

Moment Arm of Gravity

The angle of application of gravity changes with segment movement
Gravity is applied perpendicular to a segment when it's parallel to the ground
Maximal torque occurs when a body lever is parallel to the ground

Fms of Biceps & Gravity

MA of any force is greatest when the action line is at 90 degrees to its lever
Three regions: Toe region, linear region, and failure region

Tissue Homeostasis

Disruption of homeostasis by stress leads to clinical issues
Healthy individuals have a wide gap between minimal effective dose and maximal tolerated dose
Injury narrows this gap, requiring precise dosage
Goal of rehabilitation is to increase the envelope borders

Manual Loading

Mechanical forces applied during treatment
Two types: Tension loading and compression loading

Tension Loading

Forces applied in opposite directions, causing tissue elongation
Used to lengthen shortened tissue and break excessive cross-links
Examples: Traction, longitudinal, and cross-fiber stretching

Compression Loading

Forces applied into the tissue, often to the center
Shortens and widens the tissue, increasing pressure and affecting fluid flow
Facilitates fluid flow due to its pump-like effect

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Description

This quiz explores the fundamental concepts of gravitational force and the center of gravity (COG). It covers topics like the mutual attraction between objects, the significance of COG in the human body, and the line of gravity. Test your knowledge on how these concepts relate to everyday situations.