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.

Projectile motion

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 = LHOptimal angle = 45 degreesE.g. Lofted pass in football

RH>LHOptimal angle<45degrees

E.g. Shot put RH<LHOptimal 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

Golf ball Table tennis ball

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.

Fast flow – pressure lowBernoulli Principle

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

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 SpinView from sideBall DipsDecreases distances travelled

SliceView from topBall deviates right

HookView from topBall deviates left

Back SpinView from sideBall floatsIncreases distances travelled

Magnus effect

Direction of travel

Direction of spin

Direction of travel

Faster moving air creates low pressure underneath the ball

Slower moving air creates high pressure above the ball

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

Direction of travel

Magnus effect

Direction of spin

Top 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.”

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.

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

analyse

evaluatefeedback

plan

30-50%remembered

Bio-mechanics

Notation tests Question-naires

video

Technical

Tactical

Physical

Behavioural

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

Education

Transcript of Biomechanics 4