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PE 3+4 > Chapter Five : Biomechanical Principles of Equilibrium > Flashcards

Chapter Five : Biomechanical Principles of Equilibrium Flashcards

1
Q

Equilibrium definition

A

When an object has no unbalanced forces or torques acting on it
Either motionless or moving at a constant velocity

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2
Q

Static equilibrium definition

A

When an object is motionless. All the forces and torques acting on the body add up to zero

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3
Q

Three conditions for static equilibrium

A
  1. The sum of all the vertical forces acting on the body must be zero
  2. The sum of all the horizontal forces acting on the body must be zero
  3. The sum of all the torques must be zero
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4
Q

Dynamic equilibrium definition

A

When the body or an object is moving with a constant velocity

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5
Q

Stability definition

A

Is the resistance to the disruption of the equilibrium

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6
Q

Balance definition

A

Is the ability to control equilibrium while stationary or moving

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7
Q

Correlation between balance and stability

A

Higher stability objects have more balance, lower stability objects have less balance

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8
Q

Factors affecting stability

A 
Base of support
Centre of gravity
Line of gravity
Body mass
Friction between the body and the surface
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9
Q

Base of support definition

A

Is the area bound by the outside edges of the body parts in contact with the supporting surface

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10
Q

Relationship between base of support and stability

A

The larger the base of support the greater the stability

The smaller the base of support the lesser the stability

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11
Q

Increasing base of support examples

A

Boxer widening his stance
Baseball player spreading his legs
Cricketer moving one leg forward

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12
Q

Decreasing base of support examples

A

Swimmers lean on tiptoes to allow an easier takeoff in diving
A dancer on one foot has less stability to allow them to complete turns easier
Sprinter leaning on tiptoes to allow them to takeoff quickly

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13
Q

Centre of gravity definition

A

The point at which the whole weight of an object can be considered to act

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14
Q

How does the centre of gravity change?

A

When moving upwards (tiptoes) the centre of gravity moves upwards
When crouching down the centre of gravity is lowered

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15
Q

Relationship between the centre of gravity and stability

A

When the centre of gravity is raised the stability is decreased
When the centre of gravity is lowered the stability increases

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16
Q

Raising centre of gravity to decrease stability examples

A

Divers on their tiptoes to initiate diving quicker
Runners begin on their toes to initiate a quicker takeoff
Dancers perform on their toes to allow easier turns

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17
Q

Lowering centre of gravity to increase stability examples

A

Wrestler crouching down when against opponent
Surfer crouching down on the board to maintain stability
Boxer crouching down to brace himself

18
Q

Locating the centre of gravity

A

Usually sits near he navel
When the mass has uniformly distributed the centre of gravity will be in the exact centre
When the mass inst uniformly distributed the centre of gravity will shift towards the direction of greatest mass

19
Q

Line of gravity definition

A

A theoretical line that passes through the centre of gravity in the direction that gravity acts

20
Q

The relationship between the line of gravity and stability

A

When the line of gravity acts through the centre of the base of support the stability is increased
Moving the line of gravity to the edge or the outside of the base of support decreases stability

21
Q

Examples of moving the line of gravity outside the base of support

A

Swimmers leaning over on their blocks to initiate dives easier
Sprinters leaning over blocks to initiate run easier
Rugby players leaning forward to create more resistance against their opposition

22
Q

The relationship between body mass and stability

A

The greater the mass of the body the higher the stability as it requires more force to move them
The lighter the mass of the body the lower the stability as it takes less force to disrupt equilibrium

23
Q

Increasing mass for stability examples

A

A wrestler has an advantage of being heavier as it will be harder to move them
A rugby player having a greater mass will allow them to have more stability against opponents

24
Q

Decreasing mass for stability examples

A

A dancer having a lighter mass so they can perform movements easier
A gymnast having a lighter mass so they can perform movements easier

25
Q

The relationship between friction and stability

A

Increasing the friction between a body and a surface will increase stability

26
Q

Examples of increasing friction for stability

A

Surfer using wax on their board
A golfer using gloves
A footy player wearing studs on their boots

27
Q

Lever definition

A

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

28
Q

What does the mechanical advantage of a lever do?

A

Allow us to apply a small force to mover a much greater resistance
To move one point of an object a small distance, causing another point of the same object to move a relatively larger distance

29
Q

3 parts of a lever

A 
An axis (fulcrum or pivot point)
A resistance (weight or load to be moved)\
A force
30
Q

First class lever definition

A

When the resistance and the force are on either side of the axis
FAR

31
Q

Second class levers definition

A

The resistance is between the force and the axis

ARF

32
Q

Third class lever definition

A

The force is between the resistance and the axis

AFR

33
Q

Mechanical advantage definition

A

The ratio of the force arm to the resistance arm

34
Q

Mechanical advantage equation

A

Mechanical advantage = Force arm / Resistance arm

35
Q

Force arm definition

A

Is the distance from the axis to the force

36
Q

Resistance arm definition

A

Is the distance from the axis to the resistance

37
Q

Mechanical advantage values

A

> 1 - Requires less effort to move a resistance

< 1 - Increased range of motion and increases angular speed

38
Q

Lever length in sport

A

Anatomical levers are often extended through a racquet or club.
This creates a longer resistance arm
A greater force is required to move it but it increases the range of motion and therefore angular velocity allowing the ball to be hit further.

39
Q

First class lever summary

A 
FAR
force and resistance applied in same direction
MA- centre =1, resistance >1, force<1
Centre head extension
Scissors
40
Q

Second class lever summary

A 
ARF
small force needed to overcome large resistance
MA >1
resistance arm < force arm
Heel raise (axis is toe)
41
Q

Third class lever summary

A 
AFR
large forces needed to overcome small resistance
<1
force arm < resistance arm
bicep curl

PE 3+4 (16 decks)

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