Biomechanics 4

Learning Outcomes
Be able to:
• Name 3 things that effect how far a projectile
travels horizontally
• Explain what effects the optimal angle of release
• Explain what a parabola flight path is and what
causes deviations from parabola flight path.
• Apply the Bernoulli Principle to a sporting
situation
• Explain the Magnus effect with relation to the
spin placed on an object in flight.

Projectiles e.g.
• Athlete who propels themselves in to the
air such as high jumper or long jumper in
athletics
• Object hit, thrown or kicked in to the air
such as shot put, badminton shuttle,
football
• When an athlete breaks contact with the
ground or objects are released, they
become projectiles

Release of projectiles
Three factors effect the horizontal distance a
projectile travels:

• The angle of release
• The velocity at release
• The height at which released

Optimal angle of release
Depends on - release height & landing height

RH>LH
Optimal angle<45degrees
E.g. Shot put

RH = LH
Optimal angle = 45 degrees
E.g. Lofted pass in football

RH<LH
Optimal angle> 45degrees
E.g. Bunker shot in golf

Task 1
With a partner decide whether the
optimum angle of release is equal to,
less than or greater than 45 degrees.

• Racing dive in swimming
• High jump
• Hockey flick/scoop
• Long jump
• Tennis serve

Velocity of release
Increase release velocity to
increase horizontal distance
travelled
E.g.
•Speed at run up for Long
Jump
•Speed of rotation on hammer
throw

Height of release
Consider two shot putters
Providing angle and velocity
of release the same for both,
the taller shot putter will
achieve a greater distance
because of height of release.

Projectiles and forces in flight
Projectiles that have a large weight force and small air resistance force e.g.
shot puts, follow paths close to a true parabola.

Deviations from parabolic flight path
• Objects travelling at high speeds e.g. golf balls
• Objects that have large cross sectional area e.g. footballs
• Objects that do not have a smooth surface e.g. badminton shuttle
………all these incidents have distorted parabola.
……….the golf ball will follow a flight path closer to a true parabola than a table
tennis ball because it is heavier

Task 2

• Using the text books and iPads
investigate how the “Bernoulli
Principle” and the “Magnus Effect”
affect the flight path of an object
• And produce a short presentation
using Explain Everything.

Projectiles and lift
If projectile can gain some lift during flight, it will stay in the air longer and
achieve a greater horizontal distance.
Best way to introduce this is to think of an aeroplane wing and how this works.

Rounded shape pushes air over it and
makes it travel further than air
underneath the wing.

Fast flow – pressure low
Bernoulli Principle

Thought: Formula 1 cars/sports cars have a
spoiler designed to use this effect to push the car
down to stay on the track.

BERNOULLI EFFECT
• ONLY TALK ABOUT THE BERNOULLI
EFFECT IF THE OBJECT IS NOT
ROUND e.g. a discus, a javelin, a rugby
ball

Magnus Effect – types of spin
Top Spin
View from side
Ball Dips
Decreases distances travelled

Slice
View from top
Ball deviates right

Back Spin
View from side
Ball floats
Increases distances travelled

Hook
View from top
Ball deviates left

Magnus effect

Slower moving air creates high
pressure above the ball

Pressure

Direction of spin

Direction of travel

always
moves
from
high to
low –
this
causes
the ball
to dip
as it
travels

Faster moving air creates low pressure
underneath the ball

Top Spin

Magnus effect
Direction of travel

Direction of spin

The top of the ball:
• The surface of the ball is travelling in
the opposite direction to the airflow
• Causes air to slow down and causes
high pressure
The bottom of the ball:
• The surface of the ball is travelling in
the same direction as the air flow
• Causes air to speed up and causes low
pressure

Consequence:
• Pressure difference causes ball to
deviate towards the area of low
pressure.
• In the case of top spin, the ball dips
and the distance travelled is decreased
from the non-spinning flight path

Spin and Bounce – Friction important aspect!
Top Spin

• Bottom surface of ball wants
to slide backwards when
contact is made with ground
• Friction will oppose this
motion and act in a forward
direction
• This causes ball to skim off
surface quickly at a low angle
• E.g. Tennis – players like top
spin as result is ball increases
in speed as bounces allowing
a shorter time for the
opposition to hit the ball

Back Spin
• As the ball hits the ground it wants to
slide forwards
• Friction will oppose this motion and act
backwards
• This causes the ball to kick up from the
surface at a large angle to the floor
• E.g. some table tennis players can get
so much back spin on the ball, when the
ball lands it bounces back over the net
• E.g. Basketball – back spin essential to
successful shots. Will help sink the shot
after rebounding off back board. (Think
Technique of „flicking the wrist when
releasing the ball to gain back spin)
• E.g. Golf – back spin helps ball float to a
further distance and control the landing

Back Spin – Perfect Basketball shot
“Using a computer simulation of millions of
trajectories based on shots by the best
free-throw shooters, Silverberg and
colleague Chau Tran determined how
various factors affect the chance of
success.
The magic formula:
• a launch angle of 52 degrees,
• three revolutions per second of
backspin,
• and aiming for a spot 7 centimeters (2.8
inches) back from the center of the
basket, toward the back of the rim.”

THINGS TO THINK ABOUT
WHEN TALKING ABOUT
PERFORMANCE ANALYSIS

How have you applied your knowledge of
biomechanics to improve performance in your sport?
• I know what planes of movement are involved and I
have done a movement analysis & worked out which
muscles are required. I have mimicked the movements in
my training.
• Eg a football throw-in is an example of movement in the
saggital plane – the agonist muscle is the triceps and the
latissimus dorsi.
• I have used an appropriate weight training activity for the
triceps which is the triceps press in the gym. For the
latissimus dorsi I have used the Lat pull-down machine.


• Using my knowledge of levers - I have made the
best use of levers when I serve in tennis.
• I know that more power can be generated when I
use a longer lever.
• I toss the ball high and make contact with the ball
when it is as high as possible.
• This has improved the speed of my serve.

Other examples
1.Selection of
appropriate club
for a shot in golf

?

2. Cricket bowling –
releasing the ball
high in bowling


• Newton’s Laws –
1. Inertia 2. Acceleration – as a footballer - the larger the
force applied – the further the football will
travel into the opponents half.
3. Reaction – as a cricketer – the bat applies a
force in the opposite direction to the ball


• I have used my knowledge of fluid mechanics.
• As a footballer / cricketer / golfer I know that I can
use the Magnus force to change the flight of the
ball………………..example in a practical
situation: curve a free kick past defence, apply
back spin to a cricket ball, apply top spin to a
tennis serve, make a golf shot curve around a
tree

Observation & analysis
observe

plan

feedback

analyse

evaluate

30-50%
remembered

BioNotation
mechanics

Technical

Tactical
Physical
Behavioural

tests

Questionnaires

video

Possible question:
• The question might ask you to focus on
only one area………..” What methods
could you use / could the coach use to
analyse the technical aspects of a
performance?”
• For technical – talk about “the perfect
model”

Health screening & PAR-Q
• Physical Activity Readiness
Questionnaire

Field testing & Lab testing
• Numbers involved
• Cost
• Accuracy

Biomechanics 4

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