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Flashcards in U3 AOS1 Pt2 Deck (67):
1

Biomechanics

Science that studies living things from a mechanical perspective

2

What is a force

A push or pull
Mass x Acceleration

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How do forces affect objects

Change its shape (stretch, squash, twist)
Move the object (speed up, slow down, change direction)

4

Types of forces

Gravity
Weight
Friction
Drag

5

Gravity

A constant force that acts through the centre of mass of an object towards the earth
9.8m/s2

6

Friction

Occurs when two surfaces come into contact with each other, opposing the motion of an object
To start an object moving, you must overcome its friction by applying a greater force
Influenced by surface imperfections and surface area

7

Drag Force: Air and Water Resistance

Caused by the collision of air and water particles on the object, opposing its motion
Affected by air density, speed, cross sectional area of object
Increase speed means increase drag
Decrease surface area and use tight clothing

8

Weight and Mass

Mass is the amount of matter an object is made up of (kg)
Weight is the force exerted upon a body by gravity (N)
Weight = Mass x Gravity

9

Inertia

Tendency of an object to resist a change in its state of motion, whether at rest or constant velocity
Greater mass=greater inertia=greater force to move object

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Momentum

Measure of the amount of motion an object has and its resistance to changing that motion
Momentum = Mass x Velocity

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Conservation of momentum

Momentum is conserved in an isolated system where there are no external factors acting
"Total momentum of systems before the collision is equal to the total momentum after the collision'

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Summation of Momentum

- Sequential and coordinated movements of each body segment to produce maximum velocity
- Max Vel result from momentum generated from body parts closer to centre of gravity to those further away
- larger body parts moving quickly force smaller body parts to move even faster

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How to summate momentum

- use as many body parts as possible
- use stronger, larger muscles before quicker and smaller muscles
- coordinating the sequencing of body parts so momentum can be transferred from one muscle group to the next
- create a stable base of support for Movement to occur around

14

Impulse

change in momentum of an object, mass in motion
Impulse = Force x Time
Manipulating impulse can reduce injury (hands while catching)
Larger force over shorter time or smaller force over longer time

15

Newtons First Law of Motion

Law of Inertia
A body will remain at rest or in uniform motion in a straight line unless acted upon by a external force

16

Newtons Second Law

Law of Acceleration
A force applied to an object will produce a change in motion in the direction of the force applied that is directly proportional to the size of force

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Newtons Third Law

Law of Action Reaction
For every action there is an equal and opposite reaction

18

Torque

The turning effect caused by an eccentric force (one that doesn't act through the objects centre of gravity)

Force x lever arm

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Newtons First Law of Angular Motion

The angular momentum of a body remains constant unless acted upon by an external torque

20

Newtons Second Law of Angular Motion

A torque applied to an object will produce a change in angular motion in the direction of the applied torque that is directly proportional to the size of the torque

21

Newtons Third Law of Angular Motion

For every torque there is an equal and opposite torque

22

Angular momentum

Quantity of angular motion of an object

23

Moment of inertia

The resistance of an object to changes in its state of angular motion
Mass x Radius2
Product of distribution of mass of object and the axis about which it rotates

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Conservation of Angular Momentum

Angular momentum is conserved when body is in flight
As angular momentum is constant, and mass is constant, then there is a trade off between moment of inertia and velocity

25

General motion

Combination of linear and angular motion

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Linear motion

Movement of the body where all parts move in the same direction at the same time along a line
Curved line= curvilinear
Straight line= rectilinear

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Angular motion

Movement of a body part around an axis of rotation

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Projectile motion

The movement of an object through the air

29

Distance

Measures the path travelled from start to finish regardless of direction

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Displacement

Change of position from initial position to final position
Direction of motion is important

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Speed

Ratio of the distance covered to the time taken
Speed= distance/time (m/s)

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Velocity

Ratio of displacement or change in position to the time taken
Velocity = displacement/time (m/s)

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Acceleration

Change in velocity in a given period of time
Acceleration = change in velocity/change in time (m/s2)
Can be positive or negative

34

Angular distance

Sum of all angular changes the body undergoes in degrees,

35

Angular displacement

Difference between the initial and final angular position of an object in degrees

36

Angular speed

Angular distance covered divided by the time taken to complete the motion

37

Angular velocity

Rate of change of the angular displacement of a body over time

38

Angular acceleration

Rate of change of angular velocity

39

Projectile

An object or body that is launched into the air and affected by the forces of gravity and air resistance

40

Path of an object is affected by

Angle of release
Speed of release
Height of release

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Horizontal Trajectory

Projection at 0° or perfectly horizontal

42

Oblique trajectory

Occurs when the angle of projection is between 0° and 90° (parabolic)

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Vertical trajectory

Object travels straight up and down

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Best angle for covering the greatest horizontal distance

45°

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Speed of release

Greater speed of release = greater horizontal range of projectile

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Height of release

Difference between the height of projectile release from height at which it lands

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Equilibrium

When all forces and torques are balanced

48

Static equilibrium

Body/object must not be moving or rotating
-sum of all vertical, horizontal forces and torques must be zero

49

Dynamic equilibrium

When the body/object is moving with a constant velocity, no change in speed or direction

50

Stability

Resistance to the disruption of equilibrium

51

Balance

Ability to control equilibrium

52

Factors affecting stability

Base of support
Centre of gravity
Body mass
Friction between object and surface its in contact with

53

Base of Support

Generally, larger BOS the greater stability
Moving one foot behind the other increases forward/backwards stability
Moving one foot further away midline increases side to side stab
Point of contact with the supporting surface

54

Centre of Gravity

Point around which the body's weight is balanced
Usually found near naval
Lowering COG increases stability

55

Line of gravity

Direction in which the gravity acts through the centre of gravity
-when LOG acts through centre of BOS, stability increased
- stability decreased when LOG moves to outside edge of BOS

56

Body mass

Greater mass of object, greater force required to move it, greater stability

57

Friction

Increasing friction between object and surface it is contact with increases stability

58

What is a lever

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

59

Components of a lever

Axis
Resistance
Force

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1st class lever

Resistance and force applied in the same direction with axis in middle
(Seesaw, extending head)

61

2nd class lever

Resistance and force applied in opposite directions
Resistance closer to axis and force further away
(Wheelbarrow and standing on tip toes)

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Third class lever

Resistance and force applied in opposite direction
Force closer to axis and resistance further away
(Catapult, flexing elbow)

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Mechanical advantage

Ratio of force arm to resistance arm
Force arm/resistance arm
Force arm: distance from axis to force
Resistance arm: distance from axis to resistance

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Mechanical advantage greater than one

Greater force
Less force to move resistance

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Mechanical advantage less than one

Increased range of motion and angular speed

66

Lever length

Longer levers have greater inertia and therefore more difficult to swing

67

Applying spin to a ball

Applying an eccentric force (one that acts outside an objects centre of gravity) causes objects to rotate and move forward. This turning effect is known as torque