Biomechanics: Centre of Mass and Stability

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Questions and Answers

What is the centre of mass, and how is it defined?

The centre of mass is the point at which all weight is evenly distributed.

Where is the centre of mass typically located in the anatomical position?

Around the navel.

How does the centre of mass change when the body position changes?

The centre of mass also changes as the body position changes.

What is the line of gravity, and what direction does it run?

The line of gravity runs from the centre of mass vertically down to the ground. Signup and view all the answers

What is the base of support, and how does it relate to points of contact?

The base of support is the area covered between the points of contact, and points of contact are the number of body parts in contact with the surface area. Signup and view all the answers

Why is it essential to consider the centre of mass and stability in physical activities?

It is essential to consider the centre of mass and stability in physical activities because it helps us understand how to maintain balance and prevent injuries. Signup and view all the answers

How does the centre of mass change when a performer moves significant amounts of mass forward?

The centre of mass moves forward, and in some cases, it can move outside the body. Signup and view all the answers

Why is it important to consider the centre of mass in different body positions?

It is important to consider the centre of mass in different body positions because it helps us understand how to maintain balance and stability in various situations. Signup and view all the answers

What is the principle of balance that states that if your line of gravity falls within your base of support, stability is increased?

Principle of balance: If your line of gravity falls within your base of support, stability is increased. Signup and view all the answers

What is the benefit of having multiple points of contact according to the principle of balance?

The greater the points of contact, the greater the balance. Signup and view all the answers

Why does the tackler aim to put their hands behind the opponent's knees?

To squeeze and lift the opponent's front leg off the ground, reducing their points of contact. Signup and view all the answers

How does the width of the base of support affect balance?

The greater the area of support, the greater the balance. Signup and view all the answers

What is the advantage of having a lower center of mass?

The lower the center of mass, the greater the stability. Signup and view all the answers

Why do coaches encourage the tackler to get 'eyes to thighs'?

To assist the performer in getting their body lower to the ground than their opponent. Signup and view all the answers

How does mass affect stability?

The greater the mass, the greater the stability. Signup and view all the answers

What is the advantage of having a wider base of support in a tackling situation?

It provides a further competitive advantage in the contest. Signup and view all the answers

What is the result of an opponent having only one point of contact and a narrow base of support?

They will lack stability and balance. Signup and view all the answers

Study Notes

Centre of Mass (CoM)

CoM is the point where weight is evenly distributed across an object.
CoM is not a fixed point; its location varies based on body position, especially in movement.
For a human in anatomical position, the CoM is typically around the navel.
Women generally have a slightly lower CoM compared to men.

Locating the Centre of Mass

Changes in body position alter the CoM location.
In weightlifting, as weights are lifted overhead, the CoM rises due to the increased weight above the body.
When a performer shifts mass forward (e.g., extending arms or legs), the CoM also shifts forward, potentially moving outside the body's physical boundaries.

Terminology

Line of Gravity: Vertical line extending from the CoM straight down to the ground.
Base of Support (BoS): Area covered by the points of contact with the ground.
Points of Contact (PoC): Number of body parts in contact with the surface area.

Principles of Stability

A line of gravity within the BoS enhances stability.
More points of contact generally improve balance.
Coaching strategies in sports like rugby emphasize lowering the opponent's points of contact (e.g., tackling at the knees) to reduce their stability.

Factors Influencing Balance and Stability

A wider BoS increases balance, while a narrow BoS decreases it.
Lowering the CoM boosts stability; coaching tips include getting "eyes to thighs" to encourage a lower position.
A greater mass enhances stability by providing resistance against external forces, though mass isn't the sole determinant in outcomes like tackles in rugby.

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Description

Learn about the concept of centre of mass, its definition, and how to locate it in the human body. Understand the importance of centre of mass in biomechanics and its application in Physical Education.