LEWIS: Mechanics Of Movement Flashcards Preview

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Flashcards in LEWIS: Mechanics Of Movement Deck (101):
1

Linear motion is

A motion in a straight or curved line with all body parts moving the same distance at the same speed in the same direction

2

Linear motion is measured in 10 ways

Mass
Weight

Distance
Deceleration

Speed
Velocity

Inertia
Momentum

3

Scalar quantities are described in terms of

Magnitude

4

Scalar measurements:

Mass
Distance
Speed
Inertia

5

Vector quantities are described in terms of

size and direction

6

Vector measurements are

Weight
Acceleration
Deceleration
Displacement
Velocity
Momentum

7

Mass is

Body tissue
Scalar

8

Weight is the

Force on a given mass due to gravity
Vector

8

Distance and displacement are used to describe a

Body's motion

9

Inertia is the resistance

An object has to a change in its state of motion
Scalar
Newton's 1st law
Bigger the mass the larger the inertia needed

10

Distance is the length of the path a body follows when

Moving to a point
E.g. 400m rubber

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Displacement is the length of a straight line joining the

Start and finish points
E.g. 200m race on the track

12

Speed is the rate of change of

Position
Scalar

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Equation for speed =

Distance(m)/time(s)

14

Equation for velocity =

Displacement(m)/time(s)

15

Velocity is the rate of change of position with reference to

Direction
Vector

16

Acceleration and deceleration are the rate of change in

Velocity

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Acceleration =

Velocity increases

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Deceleration =

Velocity decreases

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Acceleration and deceleration =

vector

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Acceleration =

change in velocity (ms-1) / time (s)

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Change in velocity =

final velocity - initial velocity

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Momentum is the product of

mass and velocity of an object

24

Momentum (kg/m/s-1) is calculated using:

mass (kg) x velocity (m/s-1)

25

Momentum =

vector as it has magnitude and direction

26

Momentum is a closed system, which means total momentum is conserved. So when 2 objects collide the total momentum stays...

the same

27

forces can be either :

internal or external

28

internal forces are generated through the contraction of

skeletal muscles

29

external forces come from outside the body, e.g.

air resistance and friction

30

2 factors affect a generated force:

size (dependent on the size and number of muscle fibres used)
direction (force applied through the middle = move in same direction as force)

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Applying a force straight through the centre =

linear motion

32

Applying a force off-centre results in spin =

angular momentum

33

force =

mass x acceleration

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vertical forces:

weight
reaction

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horizontal forces:

friction
air resistance

36

(VF) weight is a

gravitational force that the Earth exerts on a body pulling it downwards

37

(VF) reaction occurs whenever

2 bodies are in contact with one another (Newton's 3rd law)

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(HF) Friction occurs whenever there are 2 bodies in contact with each other that try to move over one another. It acts in opposition to motion and resists the sliding/slipping motion of

2 surfaces

39

(HF) Air resistance opposes the motion of a body travelling through the

air

40

Air resistance depends on the:

-velocity of the moving body (greater velocity = greater resistance)
-cross-sectional area of the moving body (larger cross-section=greater air resistance)
-shape and surface characteristics of the moving body (streamlined = less resistance)

41

FREE BODY DIAGRAMS: (VF) Weight is always drawn

down from the centre of mass

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FREE BODY DIAGRAMS: (VF) Reaction starts from where 2 bodies are in

contact with one another, e.g. foot to floor or sports equipment and a ball

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FREE BODY DIAGRAMS: (HF) Friction starts from where 2 bodies are in contact and is opposite to the direction of any

potential slipping (usually drawn in the same direction as motion)

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FREE BODY DIAGRAMS: (HF) Air resistance is drawn from the

centre of mass and opposes the direction of motion of the body

45

Net force is the resultant force acting on a body when all other forces have bee

considered

46

Net force is often discussed in terms of

balanced versus unbalanced forces

47

Balanced force is when there are 2 or more factors acting on a body that are

equal in size but opposite in direction

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Balanced force = 0 net force and no change in motion so is directly related to

Newton's first law

49

Unbalanced is when a force acting in one direction on a body is

larger than the force acting in the opposite direction

50

Impulse is the product of the

average size of the force acting on a body and the time for which that force is applied

51

Impulse (Ns) is calculated as:

force x time

52

The longer the contact the

greater the impulse

53

impulse can be used to add speed to a body or object. Speeding up a body or object can be achieved by increasing the amount of

muscular force that is applied

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Example of greater force due to impulse =

push pass

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Speeding up of an object can be achieved by increasing the amount of time for which the force is

applied

56

Impulse is represented by a

force-time graph

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Positive impulse occurs for

acceleration at take off

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Negative impulse occurs when foot lands to provide a

braking action

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start of 100m race - the net impulse is positive, which results in

acceleration

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middle of 100m race - the net impulse is equal which results in no acceleration or deceleration, so the sprinter is running at a

constant velocity

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end of 100m race - the net impulse is negative, which results in

deceleration

62

projectile motion refers to the motion of either an object or the human body being 'projected' into the air at an

angle

63

3 factors that determine horizontal distance that a projectile can travel:

angle of release
height of release
velocity of release

64

(Angle of release) to achieve maximum horizontal distance, the angle of release of the projectile is important. The optimum angle of release is dependent upon release height and landing height. When both are equal the optimum angle =

45 degrees

65

(Angle of release) if release height = greater than the landing height, then the optimum angle of release is less than

45 degrees = shot putter

66

(Angle of release) if release height = lower than landing then the optimum angle is greater than

45 degrees = basketball set/jump shot

67

(Velocity of release) the greater the release velocity of a projectile, the greater the

horizontal distance travelled, e.g. throwing events (javelin/hammer)

68

(height of release) a greater release height results in an increase in

horizontal distance, e.g. taller = further

69

Projectiles are affected by

weight
air resistance

70

projectiles with a large weight = small air resistance and follow a

parabolic pathway

71

projectiles with a lighter mass (shuttlecock) are affected by air resistance and this causes them to deviate from

parabolic pathway

72

During parabolic pathway:
horizontal component remains:


the same throughout (point of release, highest point, point immediately before landing)

73

(PP) Vertical component
Point of release:
Highest point of flight:
Point immediately before landing:


large
none (weight and reaction force equaled)
larger due to gravity

74

Angular motion is the movement around a

fixed point or axis = somersault

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Angular motion occurs when a force is applied outside the

centre of mass

76

3 axes of rotation:

transverse = horizontal across body (somersault)
frontal = front to back (cartwheel)
longitudinal = top to bottom (spinning ice skater)

77

angular momentum depends on the

moment of inertia
angular velocity

78

Torque (moment) is a rotational force. It causes an object to turnabout its axis of rotation. Movement of a force or torque can be calculated as:

force(N) x perpendicular distance from axis of rotation (m)

79

Angular distance is the angle rotated about an axis when moving from one position to

another

80

Angular acceleration is the rate of change of velocity during

angular movement

81

angular velocity is the rate of movement in

rotation

82

angular displacement is the amount of rotation of a point, line/body in a specified direction about an

axis

83

angular momentum is conserved unless an external torque acts upon it.
Angular momentum =

angular velocity x moment of inertia

84

Newton's first law (law of inertia): a body will continue in its state of rest or motion in a straight line, unless

external forces are exerted upon it

85

NFL/LOI example = point in race where the runner has reached a

OR

Sprinter will remain in set position until force is applied to

constant velocity (80-90m in 100m)




change their state

86

Newton's second law (law of acceleration): the rate of change of momentum of a body is proportional to the force causing it and the change that takes place in the direction in which the force

force =

acts




mass x acceleration

87

NSL/LOA example = force applied to ball, acceleration is proportional to the size of the force - the harder the ball is kicked, the

sprinter = greater force (muscular) applied to blocks =

further and faster it will go



greater acceleration

88

Newton's third law (law of reaction): to every action there is an equal and opposite

reaction

89

NTL/LOR example = footballer jumps up to win a header, a force is exerted on the ground in order to gain height. At the same time, the ground exerts an upward force (equal and opposite) upon the

footballer

90

NFL on angular motion: a rotating body will continue in its state of angular motion unless an

external force (torque) is exerted upon it

91

NSL on angular motion: the rate of change of angular momentum of a body is proportional to the force causing it and the change that takes place in that direction. I.e. leaning forwards will create

more angular momentum than standing straight

92

NTL on angular motion: when a force is applied by one body to another, the second body will exert an equal and opposite force on the other body. I.e. when in a dive, when changing position from a tight tuck to a

layout position

93

inertia = resistance to change in motion
Moment of inertia (MOI) is therefore resistance of a body to

angular motion

94

The greater the mass of a body/object, the greater the resistance to change and therefore the greater the

moment of inertia

95

The closer the mass is to the axis of rotation the easier it is to turn so MOI is

low, e.g. tuck

96

increasing the distance of the distribution of mass from the axis of rotation will increase the

moment of inertia, e.g. pike/straight

97

angular momentum =

angular velocity x moment of inertia

98

angular momentum is

conserved

99

speed of a spin depends on

MOI and angular velocity

100

(Spin) increase in MOI =

decrease in AV (vice versa)

101

Ground reaction force =

the equal and opposite force given to a performer who exerts a muscular force into the ground (NTL)