Chapter 5- Biomechanical Principals of Equilibrium

Question 1

What is the equilibrium?

Answer 1

It is a state balance, in which all opposing forces or influences are balanced.

Question 2

How does the body reach static equilibrium?

Answer 2

It must be moving or rotating

Question 3

What is dynamic equilibrium?

Answer 3

It is when the body or an object is moving with a constant velocity (no change in speed or direction)

Question 4

What is stability?

Answer 4

Stability is the ability of your body to return to a desired position or trajectory following a disturbance acted on by the external forces. (a defender pushing you off a ball)

Question 5

What is balance?

Answer 5

Balance is the ability to control equilibrium in relation to gravity (holding a handstand)

Question 6

What happens when the stability of an object is increased? Give a sports example.

Answer 6

It is harder to unbalance; wrestlers increase their stability so it’s more difficult to disrupt their equilibrium

Question 7

What happens when the stability of an object is decreased? Give a sports example.

Answer 7

It is easier to unbalance; Swimmers on the blocks minimise their stability so only small movements are required to initiate the dive, to disrupt their equilibrium

Question 8

What is the rule for bases of support?

Answer 8

Generally, the larger the base of support, the greater the stability.

Question 9

Explian how the base of support works, using the example of feet

Answer 9

Moving one foot in front of the other, or widening the stance will increase the stability and the degree of muscular effort required to maintain this stability will decrease.

Question 10

What is the centre of gravity? Where is it in the human body generally?

Answer 10

The body’s centre of gravity is the point around which its weight is balanced, regardless of the position of the body (the navel)

Question 11

How can the centre of gravity change?

Answer 11

It can be raised and lowered depending on the position of the body, the higher it is the less stable it is (think cars rolling)

Question 12

Locating the centre of gravity in sports equipment

Answer 12

The centre of gravity in a perfectly symmetrical object that has constant density, mass and uniform weight distribution will be the exact centre of gravity (e.g. baseball, right in the centre). In the mass distribution in the object is not constant, the centre of gravity will shift in the direction of greater mass (e.g. gold club, closer to the bottom)

Question 13

Why is it hard to find the centre of gravity of the human body?

Answer 13

One must take into account the densities of the muscles, bone, fat and body tissue which are all unequally distributed through the body

Question 14

What is the line of gravity?

Answer 14

It is the direction in which the gravity acts

Question 15

What happens when the line of gravity ats through the centre of the base of support? What happens when it doesn’t?

Answer 15

When it does act through the centre the stability is increased. When it moves outside or to the edges of the base of support, stability is disrupted.

Question 16

How does body mass effect stability? Give a sports example.

Answer 16

The greater the mass of an object/body the greater the force required to move it, to disrupt equilibrium. Gymnasts must be light to do quick turns, rather than wrestlers that need to be heavier.

Question 17

How does friction effect stability? Give a sports example.

Answer 17

By increasing the friction between the body and the surface will increase one’s stability. Surfers wax their boards to create friction, thus increasing stability

Question 18

What is a lever?

Answer 18

A lever is a simple machine consisting of a rigid bar that can be made to rotate around an axis in order to exert a force on another object.

Question 19

What do all levers consist of?

Answer 19

a force, an axis and a resistance

Question 20

Give an example of a first class lever in the human body.

Answer 20

A head, the front is the resistance the neck is the axis and the spine and muscles are the force

Question 21

Give an example of a second class lever in the human body.

Answer 21

A foot, the toes are the axis, the resistance is the body weight on the foot and the force is the calf muscles lifting the heel

Question 22

Give an example of a third class lever in the human body.

Answer 22

A bicep curl, the force is the bicep muscles, the axis is the elbow joint and the resistanceis the weight being lifted at the wrist

Question 23

What is the mechanical advantage?

Answer 23

force arm/resistance arm

the longer the arm the higher the mechanical advantage