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KEY KNOWLEDGE
Linear motion occurring in
sport and physical activities
from the perspective of
acceleration and deceleration
and both velocity and
distance/displacement
Angular motion occurring in
sport and physical activities by
considering torque, angular
velocity, momentum and
moment of inertia.
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© Cengage Learning Australia 2011
KEY SKILLS
Correct use of terms that explain how
biomechanical principles apply to a range of
sporting movements
Investigate and interpret graphs of
biomechanical principles pertaining to
movements in sports and activities
Participate in, analyse and report on a range
of biomechanical activities
Evaluate the efficiency of various
movements by applying biomechanical
principles
Compare and contrast a variety of sports
movements and discuss the correct way
biomechanical principles can be used to
bring about improvements.
© Cengage Learning Australia 2011
Biomechanics is the study of living things from a mechanical perspective
and is essentially the physics behind human movement.
Biomechanists are responsible for:
Human performance analysis (see next slide)
The analysis of force in sport and physical activities
How injuries occur in sport
Injury prevention and rehabilitative
treatment and methods
The design and development of sporting equipment.
© Cengage Learning Australia 2011
Motion
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There are 3 basic forms of motion:
Linear motion
 Angular motion
General motion.
Linear motion:
Linear motion occurs when all the parts of an
object travel over the same distance at the same
time. E.g. Ice-skater gliding down the ice.
Curvilinear Motion:
When a curved line is evident
The flight or trajectory of a projectile is usually
in a curvilinear motion
E.g. Throwing a javelin or a long jumper
Angular motion:
Angular motion is evident
when the body or an object
turns about an axis of rotation.
The axis may be a fixed point –
for example, the shoulder joint
in a throw.
In the human body the body
parts closest to the axis of
rotation move less distance than
do the body parts furthest from
the axis of rotation.
General motion:
Angular motion tends to be far more
common in sports than linear motion.
However most sporting activities use a
combination 0f both – linear and angular
motion.
General motion:
General motion may be described as
linear motion of the whole body that is
achieved by the angular motion of some
parts of the body.
E.g.1) 100m sprint – the whole body
moves in a straight line as a result of the
angular motion of the legs about the hip
joint.
E.g.2) A cyclist pedalling and a kayaker
paddling down the river.
Distance is the path travelled from start to finish, regardless of direction.
Displacement is defined as a change in position.
© Cengage Learning Australia 2011
Speed can be calculated by dividing the distance travelled by the time it took
Velocity is equal to the time it takes to change position
Both are expressed as metres per second or m/s
1. Calculate the speed of a car if it travels 100 metres in 5 seconds.
© Cengage Learning Australia 2011
Acceleration is the change in velocity over a period of time and when positive
an object is speeding up and when negative it is slowing down.
Something with zero acceleration is simply not changing its velocity
and could be moving at a constant velocity. Expressed as m/s²
© Cengage Learning Australia 2011
Angular motion
This involves rotation around a central
axis or point (real or imaginary)
You can see these angular motions allow
the body to move in a linear way.
© Cengage Learning Australia 2011
Torque
Angular motion is caused by a force
acting outside the centre of gravity – this
is known as an eccentric force and
results in rotation known as torque.
Torque is sometimes referred to as
moment of force
Moment of force = force x lever arm
The greater the torque, the greater the
rotation/angular acceleration.
© Cengage Learning Australia 2011
Torque is affected by:
•length of level arm
•amount of force
applied
Spin is a classic example
of torque.
The bigger the lever arm
and the greater the
applied force = the
greater the amount of
spin of an object.
© Cengage Learning Australia 2011
Angular distance = the angular distance covered by a rotating body, e.g. a
gymnast doing two full rotations on the high bar would cover 360° x 2 = 720°
Angular displacement = the change between the initial and final position of a
rotating object, e.g. a gymnast doing a one and a half rotation on the high bar
would displace only 180° even though they have covered 360° + 180° = 540°.
© Cengage Learning Australia 2011
Angular speed, velocity & acceleration
Angular speed = angular distance covered ÷ time taken to complete
rotation, e.g. a gymnast doing two full rotations in 2 seconds on the high bar
would cover 360º x 2 = 720º ÷ 2 = 360º / second
Angular velocity = the rate of change of angular displacement, e.g. a
gymnast doing a one and a half rotation in 1 second on the high bar would
displace only 180º ÷ 1 = 180º / second
Angular acceleration = the rate of change of angular velocity or the rate of
change in angular velocity – this can be positive or negative (deceleration).
© Cengage Learning Australia 2011