1. ©PE STUDIES REVISION SEMINARS
2A/2B BIOMECHANICS 2nd ed.
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2. BIOMECHANICS – WHAT IS IT?
The study of motion and the effects of forces relative to the body.
Applies the laws of mechanics and physics to human performance
Contributes to the improvement in mechanical aspects and sports performance in following areas
Description
Explanation
Prediction
Improvement
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3. BIOMECHANICS – BENEFITS
Technique efficiency
Injury reduction through an understanding of injury causes and application of correct technique
Modification of sports equipment to improve sports performance at all levels
E.g. Junior size equipment made lighter and easier to use
E.g. Technological advancements in cricket bats, golf equipment, tennis racquet etc to improve power and accuracy
Technological development of equipment and computer technology to assist in transition from practice field to playing field
E.g. Bowling machine in cricket
E.g. Video software – Swinger, Dart Fish, Silicon Coach
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4. TYPES OF MOTION IN PHYSICAL ACTIVITY
“Define and apply linear motion to selected sport in relation to speed, velocity, acceleration, instantaneous measure/mean measure
Define and apply angular motion to a selected sport in relation to angular velocity
Define and apply general motion to a selected sport”
Curriculum Council of Western Australia. Physical Education Studies Support Document 2009.
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5. ©PE STUDIES REVISION SEMINARS
LINEAR MOTION
Takes place through linear pathway, either in a curved line (curvilinear)
Ball when it follows a parabolic pathway moves in a curvilinear motion
a ski jumper moving through the air in the glide phase
or a straight line (straight line motion)
All body parts travel in the same direction at the same speed.
E.g. An ice skater gliding after they completed a race (straight line motion),
Also referred to as translatory
motion, or TRANSLATION
When a body experiences
translation, it moves as a unit, and
portions of the body do not move
relative to each other
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6. ROTATIONAL (ANGULAR) MOTION
Takes place when object turns about an axis of rotation
All body parts travel through the same angle, in the same direction, in the same time
As a result, all body parts do not move through the same distance
E.g. When a gymnasts performs a giant circle on a bar, the entire body rotates, with the axis of rotation passing through the centre of the bar.
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7. ROTATIONAL (ANGULAR) MOTION
In the human body, angular motion can take place around 3 different axis of rotation
Medial axis – navel to lower back (gymnast performing cart wheel)
Longitudinal axis – head to toe vertically (ice skater spinning)
Horizontal axis – hip to hip (diver performing forward somersault)
MEDIAL AXIS
LONGITUDINAL AXIS
HORIZONTAL AXIS
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8. ©PE STUDIES REVISION SEMINARS
GENERAL MOTION
Combination of linear and angular motion
Human movement usually consists of general motion rather than pure linear motion or angular motion
E.g. a cyclist may move in a straight line as a result of the rotation of the legs about the hip joint
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9. QUANTITIES USED IN LINEAR AND ANGULAR MOTION
Linear Motion
ANGULAR MOTION
Distance: path of body as moves from one location to another
Displacement: how far you finish from start point in set direction
Speed: Distance
Time
Velocity: Displacement Time
Acceleration: Final vel – initial vel
Vector: A quantity that has both magnitude and direction
Angular distance: the exact length of an angular path
Angular displacement: the angle between the initial and final position of the body.
Angular speed: Angular distance
Time
Angular velocity: Angular displacement
Angular acceleration:
Final angular vel – initial angular vel
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10. ©PE STUDIES REVISION SEMINARS
LINEAR MOTION
DISTANCE
Path of a body as it moves from one location to another.
Measured in terms of total distance covered (42km – as per diagram)
DISPLACEMENT
Measure how far you finish from your start position in a set direction– measured in magnitude and direction (1km west – as per diagram)
Distance
6km
1km
3km
Start
5km
Finish
5km
8km
Displacement
Runner
15km
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11. ©PE STUDIES REVISION SEMINARS
LINEAR MOTION
SPEED
Movement from one point to another in the fastest possible time.
Calculated by dividing distance travelled by time taken
Distance travelled
Speed =
Time taken
100 metre sprint
Time taken = 10 seconds.
Therefore - speed = 10m/s
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12. ©PE STUDIES REVISION SEMINARS
LINEAR MOTION
SPEED
Average speed does not tell us what went on during the race itself
Does not tell us the maximum speed
reached by the racer
Does not indicate when the racer was
speeding up or slowing down.
More information is gained from looking
at intervals during a race
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13. ©PE STUDIES REVISION SEMINARS
LINEAR MOTION
VELOCITY
Speed in a given direction.
Obtained by dividing displacement by time taken.
E.g. An athlete runs 400m in 80 seconds in lane 1 of an athletics track – starts and finishes at the same spot – displacement =0.
0m m
Velocity = BUT Speed =
80sec sec
Av velocity = Av speed = 5m/s
Displacement
Velocity =
Time taken
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14. ©PE STUDIES REVISION SEMINARS
LINEAR MOTION
ACCELERATION
Rate at which the velocity of a body changes with respect to time.
Positive acceleration: Velocity is increasing
Negative acceleration (retardation): Velocity is decreasing
Zero acceleration: No change in velocity
Change in Velocity
Acceleration =
Time
Max speed
Fatigue
Positive Zero Negative
200m sprint
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15. Here we look at an example of displacement and distance using a swing
ANGULAR DISPLACEMENT
ANGULAR DISTANCE
Represents the difference in the angle between the start and end position of the body. In this example, the child starts 50 deg from where she finished so her displacement is 50 deg.
Represents the sum of all angles as a body moves from its start position to its end position
= 200 deg o o 50 30 o
Here we look at an example of displacement and distance using a swing
Start 80 o 60 o 40 o 20
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16. LINEAR vs. ANGULAR QUANTATIES
Displacement
Angular displacement
Velocity
Angular velocity
Acceleration
Angular acceleration
Force
Torque
Mass
Moment of inertia
Momentum
Angular Momentum
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