**OCR**

Biomechanics

Biomechanics

Newtons 3 Laws of Motion

First Law

The law of inertia

An object at rest will remain at rest unless acted on by an unbalanced force. An object in motion continues in motion with the same speed and in the same direction unless acted upon by an unbalanced force.

Second Law

Law of Acceleration

Acceleration is produced when a force acts on a mass. The greater the mass (of the object being accelerated) the greater the amount of force needed (to accelerate the object).

Third Law

Law of Reaction

For every action there is an equal and opposite re-action.

**Levers**

Levers

Spot the lever

Spot the lever

Spot the lever

**Thanks to**

Sir Isaac Newton

Sir Isaac Newton

Sir Isaac Newton was one of the greatest scientists and mathematicians that ever lived. He was born in England on December 25, 1643.

Newton had new ideas about motion, which he called his three laws of motion. He also had ideas about gravity, the diffraction of light, and forces. Newton's ideas were so good that Queen Anne knighted him in 1705. His accomplishments laid the foundations for modern science and revolutionized the world. Sir Isaac Newton died in 1727.

The laws that govern our planet and everything on it

Starter

Draw an image of a sprinter during the start phase of their race and then during the middle phase...

What forces are acting on the body?

How do these forces change during the race?

**Planes of Movement**

**Impulse**

**Angular Motion**

**Fluid Mechanics**

Watch the video and take any notes you wish to find out more.....

TASK 1

Learning Outcomes

Select a sporting action of your choice and then describe/explain how Newton’s Laws apply.

SOME: Discuss the relationship between each of Newton’s Laws and how this relationship influences sporting actions

MOST: Explain how each of Newton’s laws applies to sporting activity

ALL: Define Newton’s 3 laws of motion; identify an example of the existence of each law

TASK 2

TASK 3

TASK 4

**L10**

2004

2007

2013

2010

2001

TASK 1: Applying Newton's Laws

How do Newton's Laws impact on canoeing?

Exam Question - 4 Marks

Force Lines

Lines that help us demonstrate the forces acting on a body and determine what will happen as a result

Putting it all together...

Lesson 12 - Thinking Time

**L11**

**Newton's Laws and Force Lines**

The canoe will stay still in the water until the paddle is put in the water and pulled through the water.

The

faster, deeper and stronger

the paddling, the faster the movement of the canoe

in the direction in which the canoe is pulled

by the paddle.

(Left side paddling = move to right, right side paddling = move to left, paddling equally on both sides = move straight).

The paddle

exerts a downwards

and

backwards force

on the water, which exerts an

equal and opposite

forwards and upwards force on the canoe to move it.

Newton’s First Law states that ‘a body will remain at rest or at a constant velocity in a straight line unless acted upon by an external force’. It means that any object that is not accelerating has no net force acting on it – the forces cancel out. This can be applied to any athlete is stationary or maintaining a constant speed in a fixed direction. For example, a 100m sprinter in the middle phase of the race (constant velocity) or in the blocks (stationary).

Newton’s Third Law states that ‘for every action, there is an equal and opposite reaction’. This means that whenever an object exerts a force on another, then it experiences an equal forced exerted back on it in the opposite direction. Reaction forces have many applications within sport including the sprint start, jumping and kicking a ball.

Candidates will use a range of examples and credit should be given for these. It is impossible to cover all sports within the mark scheme.

Newton’s Second Law states that ‘the acceleration of a body is proportional to the force causing it, and the acceleration takes place in the direction that the force acts’. The equation used is Force = mass x acceleration. The most common example used is a sprinter accelerating from his/her blocks.

Zero Net Force = all forces cancel out

So any object is either:

Stationary or

Moving at a constant speed and direction as both the horizontal and vertical forces cancel out

shown here as the opposite force lines are the same length

• it does not matter how large the forces are... constant speed means they all cancel out

Newton's 1st Law

Reaction Force

Friction

Weight

Air Resistance

Newton's 2nd Law

Reaction Force

Friction

Weight

Air Resistance

Net force acts upon an object

• net force forward =

acceleration (+ve)

• net force backwards =

deceleration (-ve acceleration)

• net force sideways =

change of direction

force = mass x acceleration F = m x a

• so the bigger the force the bigger the acceleration

• the bigger the mass the smaller the acceleration

Here there is a net force acting forwards as the amount of force applied is greater than the resistance to that force = acceleration

Newton's 3rd Law

Reaction Force

Friction

Weight

Air Resistance

TASK 4: Annotate the swimming picture. What is happening in the picture?

Two bodies exert forces upon each other

Action and reaction are equal and opposite in direction

Action of the jumper? Ground Reaction Force?

The more you push down, the more the ground pushes you up

TASK 5: Now draw and annotate examples of forces!

• Which forces do you need to include?

• What size?

• What effect?

Starter

Have a go at any of the tasks on L12 hand out

They are designed to encourage you 'outside of the box'

Thinkers achieve more!

What do you think?

What do you wonder?

**L29**

**Newton's Laws**

**Axis of Rotation**

Welcome Back to Learning....

Starter

Work with a partner note down how Newton's 3 laws apply to a football being kicked

**L12**

Now Work as a 4 using flip chart, create a big cartoon poster to show this relationship...

TASK 1:

use the cards to label the 3 axis and 3 planes of rotation/movement

Today it is hoped you will learn....

1. What

Newton's 3 Laws of Motion

Are

ALL...

2. An

applied example

for each of Newton's Laws

3. What the

3 axis of rotation

and

3 planes of movement

are

MOST...

1. How Newton's laws can be used in a

variety of sporting contexts

2. How a coach/performer would use knowledge of

planes and axis to influence their practice

SOME...

1. To

evaluate

sporting situations in relation to the planes and axis used, linking to Newton's Laws and

methods of practice

.....

Application

TASK 2:

Using the images on page 2, identify and describe how the planes movement and axis of rotation apply to each sporting situation....

The Anatomical Position

Used to describe the human body and its movements...

then complete the table...

Build on it....

Complete the exam question as a method of reflection on today's and previous lessons

By this Friday submit 1st draft Discussion

A lever is a rigid bar that rotates around a fixed point and is used to apply force against a resistance.

Effort

Remember:

the Effort is the point where the

muscle is inserted

(all muscles insert below the joint,

except for the tricep muscle

, which inserts above the joint)

A diagram of a lever in the body;

Levers are classified according to what is in the middle of the lever (fulcrum, effort or resistance)

Three Classifications of Levers

Resistance (weight)

Effort (quadriceps insertion)

Fulcrum (knee)

Name and sketch the lever operating at the elbow – remember the tricep is the only muscle which inserts above the joint that it works

Resistance (weight)

Fulcrum (elbow)

Effort (tricep insertion point (which is above the elbow))

Task: Think of examples from sport of when a performer goes up on tip toes.

This is one of the few

2nd class levers

in the body.

Always write the words out in full – never use initials

Levers are usually a 3 mark question, marks are awarded for:

Correct terms used in diagram

Correct order of terms in diagram

Lever’s classification correctly identified

It’s what goes in the middle that matters!

Easy cheat:

Extension of the elbow = 1st Class

Plantar-flexion of the ankle = 2nd Class

All other levers = 3rd Class

Exam hints for levers

Effort Arm

Effort Arm

Name and sketch the lever operating at the knee

Effort in the middle = 3rd Class Lever

= 1st class lever

Levers in the body consist of a

muscle

, a

joint

and a

weight

being lifted

Main terms

Joint

- Fulcrum/Pivot

Muscle

- Effort

Weight

- Resistance

Resistance

Fulcrum

Effort

1

2

3

F

R

E

It’s a little rhyme!!!

Answer:

Take off in high/long jump

Diving off the blocks in swimming

Start of 100m sprint –

These are all 2nd class levers!

Starter

What do these images have in common?

Which is the odd one out??

Name and sketch the lever operating at the ankle

Reflection TASK 5

Complete the table by drawing the levers and identifying them....

**L16**

resistance

Finisher

TASK 2

TASK 3

TASK 4

Mechanical

Advantage

and

Mechanical

Disadvantage

Effort Arm

Distance between the fulcrum and the effort (muscle insertion)

Resistance Arm

Distance between the fulcrum and the resistance

=

=

Resistance Arm

Class of Lever:

3rd

Therefore 3rd class levers have a

long RESISTANCE

arm but a

short EFFORT

arm

Resistance Arm

Effort Arm

Class of Lever:

2nd

Therefore 2nd class levers have a

long EFFORT

arm but a

short RESISTANCE

arm

Resistance Arm

**L17**

Forces in Flight

A projectile follows a

parabolic curve

when it is in flight

Projectile Motion

On your curve label:

The

point of release then......

determine what factors influence how far the projectile travels.

3 factors determine how far a projectile can travel

Motion of a projectile has 2 components:

Components

which can be negligible

it is continually decreasing

E

D

C

B

A

This causes the observed parabolic flight and affects the motion components as follows:

Variations in vertical and horizontal components

Force

is not applied to objects instantaneously.

When we run, our feet are in contact with the ground for a period of time (milliseconds)

time

negative

force

positive

Small negative impulse

Large positive impulse

pos

neg

force

time

Middle of Race

Landing - negative impulse

positive

negative

force

time

End of Race

pos

neg

force

time

Exam Question

Uses familiar terms to linear motion (straight line)

Uses the word angular – meaning rotating or spinning around an axis

Key Terms

Angular momentum

= amount of motion a body has during rotation

Angular velocity

= rate of movement in rotation

Angular acceleration

= the rate of change of velocity

Moment of inertia

= resistance of body to a change of state when rotating

Moment

= force x distance from pivot to line of action of force

Gymnasts try to reduce moment of inertia by tucking up tightly

Moment of inertia is dependent on the

mass of the object

and

how the mass is distributed from the fulcrum

Angular momentum

= amount of motion a body has during rotation (angular velocity x moment of inertia)

A body which is spinning / twisting / tumbling will keep its value of angular momentum once the movement has started

If the

mass moves closer to the axis

of rotation then the

moment of inertia decreases

If the moment of inertia decreases, angular velocity must increase to conserve momentum

Increased angular velocity = increased speed of rotation

DANCER - SPIN JUMP

The movement is initiated with arms held wide - highest possible MI

Once she has taken off, angular momentum is conserved

Flight shape has arms tucked across chest - lowest possible MI

Therefore highest possible rate of spin

To stop spin – arms out to reduce angular velocity and in crease MI

A bit more complicated…..

Exam question

(c)

1 (In air / during flight) angular momentum remains constant (may be shown as straight line on graph);

2 Because there are no net external forces acting;

3 Angular momentum = angular velocity x moment of inertia;

4 A change in moment of inertia results in a change in angular velolcity (may be shown on graph);

5 Tucked somersault has smaller moment of inertia than extended;

6 Hence rotation / angular velocity is quicker in tucked somersault;

7 The problem of somersaulting is the need to complete the movement quickly / lack of time – hence tucked somersault easier to do.

Any 5 for 5 marks

Impulse

Impulse Graph

Start of Race

**Impulse**

Starter

What lever do you see here

Why is it being used?

Where else might you see it?

TASK 1

TASK 2

Practical Group Tasks

TASK 3 and 4

nb: if you get bored have a go of TASK 5 or 6!

This means

ground reaction force

is applied over a period of time

Impulse

=

force

x

time

Impulse is also a

change in momentum

(mass x velocity)

Mass stays constant so equates to acceleration

Shown on force-time graphs

Starter

TASK 1: Momentum

Positive impulse generated from push off

Negative impulse generated as footfall

The

bigger the area

.....

The bigger the

impulse

and the greater the

change of momentum

of the runner......

The greater the

acceleration

What is happening here? Refer to the net impulse and acceleration in your response....

Net impulse is positive – performer is accelerating (but not as fast as in a.

Push-off - positive impulse

What is happening here?

Positive = negative impulses

Zero impulse

No acceleration

Runner at constant velocity

What's happening here?

Net impulse is negative – performer is decelerating

Small positive impulse

Large negative impulse

b.

100m Race

Work through each of the 4 stages of a race.... Note what is happening and what the graph looks like (this one should help!)

In figure a, the area under the force–time curve is

above the horizontal axis

(and hence positive), which means the

force is acting forwards

on the runner. The force lasts for a

relatively long time

, therefore the i

mpulse is high

and positive and would cause large

forward acceleration

and

change of forward velocity

of the runner.

Explanation

AQA June 05 Question 2

(c) (i) As a sprinter accelerates along the track at the beginning of a race, they generate a large impulse. What do you understand by the term ‘impulse’? (2 marks)

(ii) Sketch and label a graph to show the typical impulse generated by the sprinter at this stage of a race (6 marks)

Jun 2005 Question 2

(c)

Impulse is force x time/force applied in unit of time;

Equates to change in momentum;

If mass constant equates to change in acceleration; max of 2 marks

(d) positive clearly larger than negative;

x axis – time;

y axis - force;

units of force shown as Newtons;

units of time shown as milliseconds/less than 1 second

time intersecting at zero on force axes;

positive and negative force axes labelled;

shape of graph - negative and positive components of force shown with negative first;

negative and positive components of force labelled; max of 6 marks

Mark Scheme

**L30**

**Projectiles**

A Somersault

Newton's Laws

Conservation of Angular Momentum

Principles of Moments

The Body in Rotation

Re-Starter

**Vectors & Scalars**

Moments tend to

turn a lever arm

: clockwise or anticlockwise

To keep the lever balanced the clockwise + anticlockwise

forces must be equal

The muscle must generate enough force to

overcome the moment of inertia

(mass x distance from resistance to fulcrum)

The further from the fulcrum, the greater force required to overcome the moment of inertia

Vertical Component is Affected by?

GRAVITY

Horizontal Component is Affected by?

FRICTION

Vertical component

The upward motion of the object

Horizontal component

The horizontal motion of the object

Applying your Knowledge

1.

Select a sport where projectiles are used

2.

Consider the technical considerations that must be taken into account by the athlete for effective performance

E.g. Angular velocity or angular momentum

What causes her to spin?

Will she spin forever?

Why?

What questions do you have?

How is she going to stop spinning?

Momentum

Velocity

Acceleration

Force

What happens if she changes shape?

Starter

In your group consider the following:

On your white board

Draw a graph

of a ball when it is in flight

Explain why

it comes back down to earth in the shape you have drawn

A ball is thrown 25m

from point A to point E

The

further the mass from the fulcrum

, the greater the moment of inertia and therefore the greater the force required to make an

object spin

or

stop spinning

Many sports require performers to attempt the

conservation of angular momentum

and minimize impact of external forces

A rotating body will continue to turn about its axis with constant angular momentum unless an external force acts upon it (Air resistance, friction and gravity)

If Moment of Inertia changes by changing body shape:

Have a go of

TASK 1

TASK 2

Have a go at any of the Exam Q's

TASK 3:

What does this mean for a shot putter?

TASK 4:

What do gymnasts do the help them spin?

Expert TASK: using the concept of momentum describe each of Newton's 3 laws

1.

2.

A rotating body will accelerate in proportion to the moment of force that is applied and in the direction in which the force is applied

3.

For every action there is an equal and opposite reaction

TASK 6: Note what happens if MI changes by changing body shape

Then angular velocity must also change

to keep angular momentum the same

If MI increases (body spread out more) then angular velocity must decrease (rate of spin gets less)

Jun 2002 Qu 1

(c) Figure 1 shows a diver performing a tucked backward one-and-one–half somersault.

Figure 1

Use figure 1 to explain why performing this dive in a tucked position is easier than performing it in an extended position (5 marks)

**Magnus Effect and Bernoulli Principle**

**L31**

**L32**

Apply what you have learned so far….

TASK 3

PROPERTIES OF FRICTION

friction depends on the force pressing the surfaces together

but not on the area of contact

FRICTION

a ball with back spin will have increased backwards friction with the ground which will cause the ball to bounce backwards form its normal path

As a ball bounces there is friction between the lowest point of the ball and the ground

BOUNCING BALLS WITH SPIN

to make the ball

spin

, it must be hit so that the contact force acts

to one side

of the centre of mass

Before a ball is hit, the predominant force acting is its

weight

- which acts through the

centre of mass

of the ball

SPINNING BALLS - HOW TO MAKE A BALL SPIN

LIFT FORCES

These forces are caused by bulk displacement of fluid and are similar to air resistance when a wing shaped object moves through the air

- discus

- ski jumper

FLIGHT AND LIFT

FLUID FRICTION (or DRAG)

this depends on laminar flow, the smooth flowing of air or water past an object

laminar means flowing in layers streamlining assists laminar flow

FLUID FRICTION

HIGH VALUES OF FLUID FRICTION

any sportsperson or vehicle moving through water will have high values of fluid friction

therefore fluid friction is the critical factor governing swimming speed

FLUID FRICTION

FRICTION

is a force which acts sideways between two surfaces which tend to slide past one another

this force enables sportspeople to accelerate, slow down, swerve, walk, run grip of footwear on floor surface

FRICTION

INERTIA

is the property of mass which means that it is hard to get a massive body moving, and also hard to stop it once it is moving

inertia is related to Newton’s First Law

once an object is moving at constant velocity it will continue to do so until a force acts on it

measured in kilogrammes kg

Using the images below, identify and describe the difference between MASS, WEIGHT and INERTIA

a ball with top spin will have friction driving forwards on the ball - making the ball travel forward of its normal path

back spin - soar

top spin - dip

side spin - slice and hook

soccer free-kicks - swerving

the direction of swerve of spinning ball is therefore in the same sense as the direction of spin

Therefore there is a reduction in pressure on this side of the ball this causes the Magnus effect force as shown

This is the Bernoulli effect applied to spinning (swerving) balls

The Magnus Effect Spin

this causes reduced pressure under the wing and hence a downward force

As layers of air flow past the wing the layers under the wing flow further and therefore faster than those over the top of the wing

FLIGHT - THE BERNOULLI PRINCIPLE

FLUID FRICTION (or DRAG)

when vortices are formed the fluid doesn’t flow smoothly

bits of fluid are flung randomly sideways

which causes drag

because bits of fluid are dragged along with the moving object (cycle helmet)

CROSS SECTIONAL AREA

This is the area of the moving object as viewed from the front

The smaller the better to reduce drag

crouching down, keep elbows in!

HIGH VALUES OF FLUID FRICTION

A cyclist travels much faster than a runner therefore has high fluid friction he or she crouches low to reduce forward cross section

The helmet is designed to minimise turbulent flow

Clothing and wheel profiles are designed to assist streamlining

use of lycra clothing

shape of sports vehicles (cars or bikes)

Wikimedia commons/Frank Steele

FLUID FRICTION FORCE DEPENDS ON:

AIR RESISTANCE or FLUID FRICTION

FLUID FRICTION (or DRAG)

this is a term applying to objects moving through fluids (gases or liquids)

the force acts in the opposite direction to the direction of motion

TASK 2: Explain what technique a mountain biker should use when cycling up hill and why.

PROPERTIES OF FRICTION

friction depends on the force pressing the surfaces together but not on the area of contact

example:

inverted wings on racing cars to increase down force on wheels this increases cornering friction between the wheels and the ground

FRICTION

weight is the predominant force experienced by objects moving freely through air flight of thrown object is a parabola if there is no air resistance

WEIGHT

is produced by the gravitational force field acting on objects or bodies it is a force which acts downwards towards the centre of the Earth

WEIGHT

WEIGHT

and

MASS

are DIFFERENT

- weight is a force produced by the gravitational force field acting on objects or bodies

- it is a force which acts downwards towards the centre of the Earth

MASS

the mass of a body or object is the same everywhere and is related to amount of matter and inertia

MASS - INERTIA

and causes the ball to

spin

this is an

eccentric force

it does not act in the

same line

as the weight

this forms a

couple

which causes a twisting torque on the ball

and creates a lift force

As it moves forward and falls through the air, it pushes aside the air creating a higher pressure underneath the object and a lower pressure over the top of the object

shot or hammer in flight

air resistance much less than weight

therefore angle of release should be around 45o

LOW VALUES OF FLUID FRICTION

low values compared with other forces (fluid friction shown in red in diagrams)

FLUID FRICTION

Fluid Mechanics

Wikimedia commons/MorganaF1

**Mass - Weight - Inertia**

**Friction**

Starter

Starter

Please share your homework with someone who was not here last lesson....

What is the difference between

mass

and

weight

?

What is inertia?

Describe the influence of

friction

and

fluid friction

on performance?

The spin takes more layers of air the long way round the ball

This means that the air travels faster round this part of the ball

TASK 1:

Complete the blanks using the word bank

TASK 2: In your group bounce a ball with either backspin or top spin

Note:

What does the ball do when it hits the ground?

Why?

How does the Magnus Effect apply here?

if the ball is spinning, this friction can be increased or reduced

Observe the video and note what you learn.....

You are going to share your learning after the video has finished....

Now explain the Bernoulli Principle to your partner

TASK: On your white board draw the motion of any ball of your choice with any spin of your choice

What is meant by the terms

mass

,

inertia

and

momentum

, and their relevance to

sporting performance

‘Everything in the universe is

lazy

; so lazy that

force

is necessary to get it on the move, when

it then travels in a

straight line

with

constant

speed; so lazy that,

once in motion

, further

force

must be applied to slow it down, stop it,

speed it up or change its direction.’

Record thoughts on page 4 of Handout

We can use a ruler to help work out the order....

Even though the examination question may ask you what lever is operating at the

ankle

, the

fulcrum is the joint at the toes

, the

effort the gastrocnemius

causing the plantar-flexion to occur and the

resistance is the weight of the body through the middle of the foot

or

Have a go at

TASK 4

Learning Outcomes

ALL: Define impulse and describe how it relates to momentum and acceleration; Draw accurately force time graphs for a 100m sprint

MOST: Explain the relevance of impulse and force time graphs to sporting performance

SOME: Use impulse and force time graphs in a variety of sporting situations, relating to both momentum and acceleration

Impulse

TASK 2: Read the paragraph and then summarise into a minimum of 3 points. Add your own sporting examples

Have you ever wondered why some people go faster down hill on their bike than you do?!

Why do some people make 'big hits' in rugby?

Why aren't all skiers massive?!

Finisher

Select one of the remaining tasks or go back to...

the

shape

and

size

of the moving object

the

speed

of the moving object

the

streamlining effect

, hence:

body position and shape for swimmer

shape of helmets for cyclists

example:

when riding a mountain bike up a steep hill

you should sit back over the rear wheel

to increase downward force on rear wheel

so that there is more friction between the rear wheel and the ground

any sprinter or game player

air resistance is usually much less than friction effects and weight

therefore streamlining is seen as less important

Body shape, cross section and clothing (surface material to assist laminar flow)

are adjusted to minimise fluid friction

Based on a key principle.....

High Velocity = Low Air Pressure

Low Velocity = High Air Pressure