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A level PE - Biomechanics > Stability and Angular Motion > Flashcards

Stability and Angular Motion Flashcards

1
Q

Define the term angular motion

A

When a body or part of a body moves in a circle or part of a circle about a point (axis of rotation)

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2
Q

What is centre of mass?

A

The point at which the body is balanced in all

Directions

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3
Q

Define the term stability

A

The ability of a body to return to equilibrium or its original position after being displaced

A more stable body is harder to move

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4
Q

Describe 4 ways to maximise stability

A

Lower centre of mass
Increase size of base of support
Make line of gravity central to base of support
Increase body mass or inertia

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5
Q

What is a fulcrum?

A

A fixed point of rotation about which the lever moves

E.g - joint

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6
Q

What is the effort in a lever system?

A

The force being applied that causes the lever to move

E.g muscle

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7
Q

What is stability?

A

the ability of a body to return to equilibrium after being displaced

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8
Q

What is equilibrium?

A

a body is in equilibrium when the net force is 0 (all forces are equally balanced)

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9
Q

What is the centre of mass?

A

the point at which the body is balanced in all directions

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10
Q

Identify the factors that affect stability

A

height of centre of mass
size of base of support
line of gravity in relation to base of support
body mass or inertia

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11
Q

how does height of centre of mass affect stability?

A

the lower the centre of mass, the greater the stability

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12
Q

how does size of base of support affect stability?

A

the greater (wider, or more points in contact with the floor) the base of support, the greater the stability

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13
Q

how does the line of gravity in relation to base of support affect stability?

A

if the line of gravity is central to the base of support, stability is greate

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14
Q

how does mass / or inertia affect stability?

A

the greater your mass / inertia, the greater your stability as more force is required to move you

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15
Q

In a lever system in the body, what acts as a fulcrum?

A

a joint

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16
Q

In a lever system in the body, what acts as a load?

A

the weight to be moved (body part or object)

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17
Q

In a lever system in the body, what acts as the effort?

A

muscles

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18
Q

What is in the middle of a first class lever?

A

fulcrum

19
Q

What is in the middle of a second class lever?

A

load

20
Q

What is in the middle of a third class lever?

A

effort

21
Q

Give an example if a first class lever in the body

A

neck extension
E = trapezius
F = joint between atlas and skull
L = weight of head

22
Q

Give an example of a second class lever in the body

A

elbow in an overarm throw
F = elbow joint
L = weight of lower arm and ball in hand
E = triceps muscle

23
Q

Give an example of a third class lever in the body

A

standing on tiptoes when jumping up
F = joints between metatarsals and phalanges
E = gastrocnemius
L = weight of body

24
Q

What is a load arm?

A

the perpendicular distance of the load fro the fulcrum

25
Q

What is an effort arm?

A

the perpendicular distance from the effort to the fulcrum

26
Q

What is meant by the term ‘mechanical advantage’?

A 
if you have a mechanical advantage it means that the lever system can move a large load with a relatively small effort.
It occurs in a 2nd class lever system where the effort arm is greater than the load arm
27
Q

What is meant by the term ‘mechanical disadvantage’?

A 
Mechanical disadvantage means that the effort would need to be considerably bigger than the load in order to move the load. 
It occurs in a third-class lever system where the load arm is greater than the effort arm
28
Q

What is moment of force / torque?

A

the effectiveness of a force to produce rotation about an axis.
Moment of force = force x perpendicular distance from fulcrum (Nm)
the bigger the force or further away it is from the axis, the bigger the moment of force
Longer effort arm = greater acceleration (mechanical advantage)

29
Q

What is an axis of rotation?

A

an imaginary line or point about which the body or part of the body rotates

30
Q

where is the longitudinal axis?

A

it runs top to bottom passing through the centre of mass

a pirouette would turn about this axis

31
Q

Where is the transverse axis?

A

it runs left to right passing through the centre of mass

a somersault would turn about this axis

32
Q

Where is the frontal axis

A

it runs front to back, passing through the centre of mass

a cartwheel turns about this axis

33
Q

What is a radian?

A

the unit of measurement for angular distance and angular displacement
1 rad = 57.3 degrees (roughly)

34
Q

Describe the angular analogue or Newton’s 1st Law

A

Inertia - a body at rest will not rotate unless a force is acted upon it. A rotating body continues to turn about its axis with constant angular momentum unless acted upon by an external force

35
Q

what is angular distance?

A

the angle through which the body has rotated about its axis (rad)

36
Q

what is angular displacement?

A

the shortest change in angular position from start to finish (rad)

37
Q

what is angular speed?

A

the angular distance travelled in a certain time (rad/s)

38
Q

what is angular velocity?

A

the angular displacement travelled in a certain time (rad/s)

39
Q

what is angular acceleration?

A

the rate of change of angular velocity (rad/s/s)

change in angular velocity / time taken

40
Q

What is angular momentum?

A

the quantity of angular motion possessed by a rotating body.

angular momentum = moment of inertia x angular velocity

41
Q

what is moment of inertia?

A

the resistance of a rotating body to change its state of angular motion

42
Q

What factors affect moment of inertia?

A
  • mass of body

- distribution of mass from axis of rotation

43
Q

How does mass affect moment of inertia?

A

the bigger the mass, the greater the moment of inertia (e.g. the bigger you are, the more torque (force) you need to move you)

44
Q

How does distribution of mass from axis of rotation affect moment of inertia?

A

the further the distribution of mass from the axis of rotation, the greater the moment of inertia (e.g. the more spread out your arms and legs, the more torque (force) you need to turn)

A level PE - Biomechanics (3 decks)

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