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A2 PE
The Mechanics of Movement
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Linear Motion
Newton’s Laws of Motion
Force
Projectiles
Angular momentum
Angular velocity
LINEAR MOTION
Linear motion is when there is motion in a straight or curved line, with all body parts moving
the same distance at the same speed in the same direction
Example
Tobogganing - This moves in a straight line, the same distance, in the same direction at the
same speed.
Shot putt - The shot moves in a curved line, the same distance, direction and speed
Vector v scalar quantities
1. Scalar quantity
This is when measurements are described in terms of size or magnitude –
mass, inertia distance and speed
2. Vector quantity
This is when measurements are described in terms of size and direction –
weight, acceleration, deceleration, displacement, velocity and momentum
Vector v scalar quantities
Scalar quantities. – have magnitude (…………) only
Vector quantities – have both magnitude (size) & ………………..
A car is travelling at 30 mph.
In this instance a scalar quantity has been described. There is speed but no information regarding
its direction.
Now consider this same car travelling at 30 mph in a north-easterly direction. We now have speed
and direction: a vector quantity (velocity) has just been described.
MASS v WEIGHT
………………….. - is the quantity of matter a body possesses.
A shot putt has a greater mass than a table tennis ball as it is greater in both density and volume.
Mass only has size (no direction) and so is a scalar quantity.
………………….. - is the force, which a given mass feels due to gravity
Weight is a force and is measured in Newtons .
As weight always acts downwards from the centre of mass it has a direction as well as a size .
Weight is therefore a vector quantity.
LINEAR MOTION
Linear motion is when there is motion in a ……………or ………………. line, with all body …………..
moving the same distance at the same ……………. in the same ………………..
Example
Tobogganing - This moves in a straight line, the same distance, in the same direction at the
same speed.
Shot putt - The shot moves in a curved line, the same distance, direction and speed
Vector v scalar quantities
1. ………………….. quantity
This is when measurements are described in terms of s................ or magnitude –
mass, inertia distance and speed
2. ………………… .. quantity
This is when measurements are described in terms of s............. and dir..................... –
weight, acceleration, deceleration, displacement, velocity and momentum
Vector v scalar quantities
Scalar quantities. – have magnitude (size) only
Vector quantities – have both magnitude (size) & direction
A car is travelling at 30 mph.
In this instance a scalar quantity has been described. There is speed of the car but no information
regarding its direction.
Now consider this same car travelling at 30 mph in a north-easterly direction. We now have
information of speed and direction: a vector quantity (velocity) has just been described.
MASS v WEIGHT
Mass - is the quantity of matter a body possesses.
A shot put has a greater mass than a table tennis ball as it is greater in both density and volume.
Mass only has size (no direction) and so is a scalar quantity.
Weight - is the force, which a given mass feels due to gravity
Weight is a force and is measured in Newtons .
As weight always acts downwards from the centre of mass it has a direction as well as a size.
Weight is therefore a vector quantity.
Inertia
Inertia - is the reluctance of a body to mo……………… or change its state of m……………...
The bigger the mass of an object the harder it is to move or change its motion and therefore the
larger its inertia.
Example
A sumo wrestler has a large amount of inertia and is therefore difficult to move.
Distance v displacement
Distance – a measure of the p…………….. a body takes in moving from one position to another.
Displacement – the sh…………………possible route between the starting and finishing point of a
body that has mo………………... This will normally be in a straight line
For example, consider a 400m runner who has just completed a race. She has just covered a
distance of 400m but because the start and finish line are in the same place her displacement
is in fact zero.
Inertia
Inertia - is the reluctance of a body to move or change its state of motion.
The bigger the mass of an object the harder it is to move or change its motion
And the larger its quantity of inertia.
A sumo wrestler has a large amount of inertia and is therefore difficult to move.
Distance v displacement
Distance – a measure of the path a body takes in moving from one position to another.
Displacement – the shortest possible route between the starting and finishing point of a body
that has moved. This will normally be in a straight line
For example, consider a 400m runner who has just completed a race. She has just covered a
distance of 400m but because the start and finish line are in the same place her displacement
is in fact zero.
Speed v Velocity
Speed - is the rate of change of d……………………
• speed is therefore a scalar quantity.(size only)
• speed (ms–¹) = Distance (m) / Time (s)
velocity – is the rate of change of disp………………………..
• velocity is a vector quantity (size & direction) (ms–¹)
Acceleration Deceleration & Momentum
Acceleration or deceleration - is the rate of change of v…………………………
• Acceleration is a vector quantities (ms–2) = velocity (m/s) / Time (s)
Momentum - is the amount of mot……………………….. a body possesses
• Momentum (kgms–¹) = Mass (kg) × Velocity (ms–¹)
Speed v Velocity
Speed - is the rate of change of distance
• speed is therefore a scalar quantity.(size only)
• speed (ms–¹) = Distance (m) / Time (s)
velocity – is the rate of change of displacement
• velocity is a vector quantity (ms–¹) (size and direction)
Acceleration Deceleration & Momentum
Acceleration or deceleration - is the rate of change of velocity
• Acceleration is a vector quantities
• Acceleration (ms–2) = velocity (m/s) / Time (s)
Momentum - is the amount of motion a body possesses
• Momentum (kgms–¹) = Mass (kg) × Velocity (ms–¹)
Impulse
Impulse - is concerned with the length of t…………….. a force is applied to an o……………… or body
• Impulse relates to a change in momentum
• Impulse = force × time
Force = m…………. x a………………………… (F=ma)
• Impulse (Ft) is therefore equal to a change in momentum.
Impulse is used in sporting activity to:
• Add s……………… to a body or object
• slow d……………………. moving bodies slowly on impact.
Example
As the sprinter drives out of the blocks a large positive impulse is produced which allows the
sprinter to accelerate.
Impulse
Impulse - is concerned with the length of time a force is applied to an object or body
Impulse relates to a change in momentum that occurs as a consequence.
• Impulse = force × time
Force = mass x acceleration (F=ma)
• Impulse (Ft) is therefore equal to a change in momentum.
Impulse is used in sporting activity to:
• Add speed to a body or object
• slow down moving bodies slowly on impact.
Example
As the sprinter drives out of the blocks a large positive impulse is produced which allows the
sprinter to accelerate.
Quantities of linear motion
Complete the table below by placing a tick () in the appropriate box to identify whether
each of the quantities listed is a vector or scalar quantity.
Quantity
Vector Scalar
Inertia - is the reluctance of a body to move or change its state of
Acceleration - is the rate of
motion
change of velocity
Mass - is the quantity of matter a body possesses
Speed - is the rate of change of distance
Displacement - the shortest possible route between the starting and finishing
Momentum -
point of a body that has moved
is the amount of motion a body possesses
Weight - is the force which a given mass feels due to gravity
Velocity - is the rate of change of
displacement
Distance - a measure of the path a body takes in moving from one position to
another.
Quantities of linear motion
Complete the table below by placing a tick () in the appropriate box to identify whether
each of the quantities listed is a vector or scalar quantity.
Quantity
Vector Scalar
Inertia - is the reluctance of a body to move or change its state of
Acceleration - is the rate of

motion
change of velocity

Mass - is the quantity of matter a body possesses

Speed - is the rate of change of distance

Displacement - the shortest possible route between the starting and finishing
Momentum -
point of a body that has moved
is the amount of motion a body possesses


Weight - is the force which a given mass feels due to gravity

Velocity - is the rate of change of

displacement
Distance - a measure of the path a body takes in moving from one position to
another.

Briefly outline the differences between the following quantities of linear motion:
Mass and weight
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Distance and displacement
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Speed and velocity
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Newton’s 1ST Law of Motion–
the law of inertia
‘ Every body continues in a state of rest or motion in
a straight line, unless compelled to change that
state by external forces exerted upon it.’
EXAMPLE - In a penalty, the ball (body) will remain on
the spot (state of rest) unless it is kicked by the
player (an external force is exerted upon it)
Give an example of your own
Newton’s 2nd Law – the law of acceleration
‘The rate of change of momentum of a body is
proportional to the force causing it and takes place in
the direction in which the force acts.’
EXAMPLE - When the player kicks (force) the ball during the game, the
acceleration of the ball (rate of change of momentum) is proportional to
the size of the force. So, the harder the ball is kicked the further and
faster it will go.
Give an example of your own
Newton’s 3rd Law Law of reaction
‘To every action there is an equal and
opposite reaction’.
EXAMPLE – When a footballer jumps up (action) to win a header
a force is exerted on the ground in order to gain height. At
the same time the ground exerts an upward force (equal and
opposite reaction) upon the footballer.
Give an example of your own
Exam question
Newton’s Laws
Use Newton’s Three Laws of Motion to explain the following;
1. How does the high jumper takes off from the ground? (6 marks)
2. How does a skier stop at the end of a downhill race? (6 marks)
Newton 1st
(inertia)
Newton’s 2nd (acceleration)
Newton’s 3rd (reaction)
High
ump
A high jumper’s body will
remain motionless (in a state
of rest) unless he/she uses
muscular force (an external
force ) to start their run up.
As the high jumper approaches
the bar he/she will increase the
forward force applied to the
ground thereby increasing their
acceleration in the same
direction as the applied force.
When a high jumper uses his/her leg muscles
to exert a downward force on the ground, the
ground in-turn exerts an equal and opposite
upwards reaction force on the jumper. The
greater the force applied by the jumper on the
ground the greater the reaction force and the
higher he/she will jump.
ow does a
etball player
void
reaking the
ootwork rule
when
anding after
aving caught
he ball?
Without muscular force
applied by the player (external
force) to the court, the player
will continue to travel
forwards with the same
velocity.
The larger the force applied to
the ground, the quicker the
player will stop.
The player exerts a force on the court in the
forward direction so that the court exerts an
equal and opposite force to push them
backwards.
Football
In a penalty, the ball (body)
will remain on the spot (state
of rest) unless it is kicked by
the player (an external force is
exerted upon it)
When the player kicks (force) the
ball during the game, the
acceleration of the ball (rate of
change of momentum) is
proportional to the size of the
force. So, the harder the ball is
kicked the further and faster it
will go.
When a footballer jumps up (action) to win a
header a force is exerted on the ground in
order to gain height. At the same time the
ground exerts an upward force (equal and
opposite reaction) upon the footballer.
How does
rugby
player
ide step
o avoid a
ackle?
The player will continue in a
forward direction until he
applies muscular force to the
ground in a right side
direction, to change his
direction to move to the left
The greater the force generated,
the faster the acceleration of the
rugby player to the left hand
direction.
In side stepping to their left, the rugby player
pushes right with their right foot. This applies
a force to the right on the ground, which in
turn applies an equal and opposite force to
the left on the rugby player.
Apply Newton’s three Laws of Motion to the following sporting situations:
Sporting
situations
a high
jumper
performing a
jump
a gymnast
performing a
vault
a high diver
performing a
dive
a football
player taking
a penalty.
Newton’s 1st
Every body
continues in a state of rest or
motion in a straight line, unless
compelled to change that state
by external forces exerted upon
it.’
Newton’s 2nd
The rate of change of momentum of a
body is proportional to the force causing it and takes place
in the direction in which the force acts.’
Newton’s 3rd To every action there is an equal
and opposite reaction’.
1st Law of Motion
2nd Law of Motion
3rd Law of Motion
High jump
performing
a jump
At take off the high
jumper applies a force
to the floor to change
the direction of motion
The upward acceleration of the
high jumper is proportional to
the force produced at take off and
occurs in the direction the force acts
(i.e. upwards)
At take off the high jumper applies a larg
muscular force on to the track which
applies a force equal in magnitude but
opposite in direction from the track on t
the high jumper propelling them upward
A high diver
performing
a
dive
In order to overcome
inertia the diver applies
a muscular force on to
the diving board/platform
The acceleration of the diver
during the dive is proportional to
the amount of force applied to
the diving board and takes place
in the direction the force acts
In order to dive forwards the swimmer
applies a downwards and backwards for
on to the diving board / platform. The
diving board / platform applies an equal
and opposite force propelling the diver
forwards and upwards
A gymnast
performing
a
vault
The gymnast applies a
force to the vaulting
horse which changes
their state of motion
The upward acceleration of the
gymnast is proportional to the
force applied to the vaulting
horse and occurs in the direction
the force acts (i.e. upwards and
forwards)
During the vault the gymnast applies a
large muscular force on to the vaulting
horse which applies a force equal in
magnitude but opposite in direction from
the horse on to the gymnast propelling
them upwards and forwards
A footballer
taking a
penalty in
football
To start his run up, the
footballer must first
overcome his inertia by
applying a force to the
football pitch
The acceleration of the ball is
proportional to force applied to it
from the footballer’s muscles.
Furthermore the acceleration
takes place in the direction
which the force acts.
During the contact phase the footballer
applies a force to the ball. The ball appli
a force back on to the footballer’s boot t
is of equal magnitude but opposite in
direction. Because the footballer is heav
than the football, the ball is driven
The role of force in sporting activity
Force – is a push or pull that alters the state of motion of a body
•
When a force is applied to an object, the velocity of that object changes. This change in velocity constitutes an
acceleration. So, forces are tied to accelerations.
Forces can therefore:
1. Cause a body at rest to m....................
•
A swimmer on the blocks at the start of a race needs to apply a force on the blocks to initiate the dive
after the gun.
•
A football will remain at rest on the penalty spot until the force of the footballer’s boot on the ball
causes it to move.
2. Cause a moving body to a...........................
•
A penalty taker when they are approaching the ball. After initially starting to move, he/she can
accelerate towards the ball by applying a large force on the ground.
3. Cause a moving body to d.............................
•
If the footballer scores a goal, the force of the net at the back of the goal on the ball will cause it to
slow down.
4. Cause a moving body to change d.............................
•
If the ball is travelling towards the goal and the goalkeeper makes a save, the force exerted by the
hands of the goalkeeper will push the ball away in the opposite direction.
•
A swimmer applies a force on the wall during the tumble turn to change direction and swim back the
other way.
5. causes a body to change s...................
A swimmer applies a force to the water when entering after a dive this causes a disturbance to the water.
The role of force in sporting activity
Force – is a push or pull that alters the state of motion of a body
•
When a force is applied to an object, the velocity of that object changes. This change in velocity constitutes an
acceleration. So, forces are tied to accelerations.
Forces can therefore:
1. Cause a body at rest to move
•
A swimmer on the blocks at the start of a race needs to apply a force on the blocks to initiate the dive
after the gun.
•
A football will remain at rest on the penalty spot until the force of the footballer’s boot on the ball
causes it to move.
2. Cause a moving body to accelerate
•
A penalty taker when they are approaching the ball. After initially starting to move, he/she can
accelerate towards the ball by applying a large force on the ground.
3. Cause a moving body to decelerate
•
If the footballer scores a goal, the force of the net at the back of the goal on the ball will cause it to
slow down.
4. Cause a moving body to change direction
•
If the ball is travelling towards the goal and the goalkeeper makes a save, the force exerted by the
hands of the goalkeeper will push the ball away in the opposite direction.
•
A swimmer applies a force on the wall during the tumble turn to change direction and swim back the
other way.
5. Cause a body to change shape.
A swimmer applies a force to the water when entering after a dive this causes a disturbance to the water.
Understanding net force – balanced v unbalanced
B…........... forces - Where two or more forces act that are of e............ size but
•
•
opposite in d..........................
All the forces can.............. each other out, there is zero net
force.
An object or body will either remain stationary or if moving will continue to do
so at constant v............................
A sprinter running at constant velocity does so because there is z............ net
force acting.
Un b………………….. forces - Occur where a force acting in one direction is
larger than that acting in the opposite direction the object or body will start to
move or accelerate/ decelerate in the direction of the bigger force.
A high jumper is able to accelerate upwards because the reaction force is greater
than the weight force,
Two rugby players running towards each other in a tackle one will push the
other over
Understanding net force – balanced v unbalanced
Balanced forces - Where two or more forces act that are of equal size but
•
•
opposite in direction.
All the forces cancel each other out, there is zero net force.
An object or body will either remain stationary or if moving will continue to do
so at constant velocity.
A sprinter running at constant velocity does so because there is zero net force
acting.
Unbalanced forces - Occur where a force acting in one direction is larger than
that acting in the opposite direction the object or
body will start to move or accelerate/ decelerate in
the direction of the bigger force.
A high jumper is able to accelerate upwards because the reaction force is greater
than the weight force,
i.e. reaction force = weight force + applied muscular force.
TYPES of FORCE
Vertical forces
1. Weight: (acts d………………………)
Weight = mass × acceleration due to gravity (10ms²)
Weight always acts downwards (from the centre of mass of an object or body)
towards the centre of the earth.
2. Reaction force: (usually acts u………………………………)
• Newton’s third law - every action has an equal and opposite reaction.
• Reaction forces will therefore always occur whenever two bodies are in
contact with one another.
TYPES of FORCE
Horizontal forces
Friction: friction opposes m………………………..
Friction is actually a force that appears whenever two things rub against each other or slide over
one another.
1. The roughness of the sur……………………… in contact – the greater the friction,
• football studs or spikes worn by athletes are designed to increase friction.
2. The greater the down force or m……….. of an object the greater the friction.
• A mountain biker will sit back over the driving wheel when riding up a muddy slope in order
to gain a better grip of the tyre on the surface.
3. Wa…………….. of surfaces – dependent upon the surface this will either increase or decrease
friction.
• Consider the metal blade of an ice skate moving over the ice, for example. This will heat up
and create a thin film of water which decreases the friction between the two surfaces.
TYPES of FORCE
Horizontal forces
Friction: friction opposes motion.
Friction is actually a force that appears whenever two things rub against each other or slide over
one another.
1. The roughness of the surfaces in contact – the greater the friction,
• football studs or spikes worn by athletes are designed to increase friction.
2. The greater the down force or mass of an object the greater the friction.
• A mountain biker will sit back over the driving wheel when riding up a muddy slope in order
to gain a better grip of the tyre on the surface.
3. Warmth of surfaces – dependent upon the surface this will either increase or decrease
friction.
• Consider the metal blade of an ice skate moving over the ice, for example. This will heat up
and create a thin film of water which decreases the friction between the two surfaces.
TYPES of FORCE
4. Air r…….....… Air resistance is a form of fluid friction and therefore opposes motion.
The degree of air resistance (drag) experienced by sports performers such as
swimmers, cyclists, motor racers and skiers very much depends upon the following:
• The v………………… of the moving body – the faster an object is moving the more it is
subject to the effects of air resistance.
• The frontal cross-s………………….area of the moving body – the larger the frontal
cross sectional area the greater the effects of air resistance.
• The s……………. and surface of the moving body – the less streamlined and rougher
the surface of the moving body the more it will be affected by air resistance and
drag.
A force can be either internal or external.
I.......................forces are provided by ..................... contraction.
Can you think of and write down a sporting example where internal force acts
E ...................... forces include:
G..................... – the force that draws all bodies t....................... the centre of the earth.
Can you think of and write down a sporting example where gravity acts
A.............. R………………….......- this opposes the motion of objects through the a.................
Can you think of and write down a sporting example where air resistance acts
F.....................- the resistance to motion caused by contact between two surfaces.
Can you think of and write down a sporting example where friction acts
R........................– for every action force there must be a reaction force equal and opposite to it.
Can you think of and write down a sporting example where reaction acts
A force can be either internal or external.
Internal forces are provided by muscular contraction.
Can you think of and write down a sporting example where internal force acts
External forces include:
Gravity – the force that draws all bodies towards the centre of the earth.
Can you think of and write down a sporting example where gravity acts
Air resistance - this opposes the motion of objects through the air.
Can you think of and write down a sporting example where air resistance acts
Friction - the resistance to motion caused by contact between two surfaces.
Can you think of and write down a sporting example where friction acts
Reaction – for every action force there must be a reaction force equal and opposite to it.
Can you think of and write down a sporting example where reaction acts
Motion
1.
2.
L................ motion - is motion along a straight line where all body parts are moving the same distance, in the same
direction and at the same time. This line can be a straight line or a curved line.
A............................ motion - is when a body or part of a body moves in a circle, or part of a circle, about a particular
point called the axis of rotation.
3. G ......................... motion General motion is a combination of linear motion and circular motion.
Motion
sporting examples
Linear
Toboggan travelling down the track
Luge (skeleton bob)
Downhill Skiing travelling in a straight line down the ski slope
Water skiing in a straight line
Skating in a straight line
Angular
Gymnastics (men) one arm giant circle on a high bar
Cycling - the legs of the cyclist rotate in circles
Somersault (horizontal plane)
Ice skater performing spins (vertical plane)
Gymnastics (men’s flares) on a pummel horse
General
Swimming – arms are fully rotating about the shoulder joint in the front crawl, legs are partially
rotating about the hip joint, and the body is moving in a straight line (linearly)down the pool
Cyclist – Legs of the cyclist are rotating fully about the hip joint while the body is moving in a straight
line (linearly) down the track.
Sprinter – Arms and legs rotate about the shoulder and hip joints respectively body is moving linearly
Angular Motion
Position
Longitudinal
axis
Horizontal
/transverse axis
Frontal axis
Angular movements
possible at joint
Sporting example
Angular Motion
Position
Angular movements
possible at joint
Sporting example
Longitudinal
axis
Runs through the body or
joint from top to bottom
Rotation
Pronation
Supernation
Spinning ice skating
Horizontal axis
Runs through the body or
joint from side to side
Flexion
Extension
Front/back somersault
high dive
Frontal axis
Runs through the body or
joint from front to back
Adduction
Abduction
A gymnast performing
a cartwheel or side
somersault
Exam Questions
1. Use Newton’s Laws of motion to explain the motion of a high jumper at take-off
2. Draw a stick figure diagram showing the vertical forces acting on a high jumper at take-off.
With reference to your diagram explain what is meant by a net force. (p87 text book)
3. Define momentum of a down hill skier who has a mass of 85kg and is travelling at a velocity
of 42m/s
4. Air resistance is a force that acts against a moving body. How might a track cyclist attempt to
reduce the size of this force.
5. Name the three axis of rotation. Give an example of a skill where a rotation about each of
these three axis occurs.
Answers
1. High jump (at take off)
st
Newton’s 1
At take off the high jumper applies a force to the floor to change the direction of motion
nd
Newton’s 2
The upward acceleration of the high jumper is proportional to the force produced at take off and occurs in the
direction the force acts (i.e. upwards)
rd
Newton’s 3
At take off the high jumper applies a large muscular force on to the track which applies a force equal in size but
opposite in direction from the track on to the high jumper propelling them upwards.
2. The vertical forces acting on a high jumper at take-off are
•
weight force (downwards)
•
Reactional force (upwards)
A net force means the high jumper is able to accelerate upwards because the reaction force is greater than the
weight force this is an unbalanced force ie; (reaction force = weight force + applied muscular force) .
(p87 text book)
3. Momentum - is the amount of motion a body possesses Mass (kg) × Velocity (ms–¹)
• Momentum = kgms–¹) = 85 x 42 = Kgm/s
4. Air resistance is a force that acts against a moving body. How might a track cyclist attempt to reduce the size
of this force.
•
The cyclist will adopt a streamline body position on the cycle and wear a streamline helmet to reduce the
effects of air resistance.
5. Axis of Rotation
Longitudinal axis – spinning ice skater
•
Horizontal /Transverse axis – high diver performing a sommersault
•
Frontal axis – gymnast performing a cartwheel
Projectile motion
This section looks at the motion of objects in f................, such as human bodies high jump, throwing
implements (shot, discus, javelin or h.....................), and
football, rugby, cricket, tennis or g.............. balls.
In the air the flight of projectiles are only subject to air r................. and w..................
• If weight were the only force acting, the flight path would be para..................... in shape, (shot or
hammer, the human body in jumps or tumbles or dives). Air R..................... has minimal effect on
these objects
• For other objects such as a shuttlecock or table tennis ball the effect of air resistance is g.................
causing the projectile to veer away from the normal para..................... path.
Three factors determine the distance travelled by a projectile such as a shot;
• the v............................of release
• the a.........................of release
• and the h……..……......of release.
Generally an increase in velocity and height of release will increase the hor................... d.............
travelled by a shot putt.
There is always an optimal release angle for any height and velocity of release which maximises the
distance an object will travel.
Optimal angles of release
Where (release height .....landing height) the optimal angle of release = 45 degrees – lofted pass in football
Where (release height is ........ landing height) optimal angle of release = less than 45 degrees – shot putt
Where (release height is ........ landing height) optimal angle of release=45 degrees –free throw in basketball
Projectile motion
This section looks at the motion of objects in flight, such as human bodies high jump, throwing
implements (shot, discus, javelin or hammer), and football, rugby, cricket, tennis or golf balls.
In the air the flight of a projectiles are only subject to air resistance and weight
• If weight were the only force acting, the flight path would be parabolic in shape, (shot or
hammer, the human body in jumps or tumbles or dives). Air resistance has minimal effect on
these objects
• For other objects such as a shuttlecock or table tennis ball the effect of air resistance is
greater causing the projectile to veer away from the normal parabolic path.
Three factors determine the distance travelled by a projectile such as a shot;
• the velocity of release
• the angle of release
• and the height of release.
Generally an increase in velocity and height of release will increase the horizontal distance
travelled by a shot putt.
There is always an optimal release angle for any height and velocity of release which maximises
the distance an object will travel.
Optimal angles of release
Where (release height = landing height) the optimal angle of release = 45 degrees – lofted pass in football
Where (release height is > landing height) optimal angle of release = less than 45 degrees – shot putt
Where (release height is < landing height) optimal angle of release=45 degrees –free throw in basketball
The flight path of a shot putt
Components of velocity during flight
Near the s…………………….. of the flight:
• There is a large upward vertical component.
• But a fixed horizontal component.
At the m…………………………. of the flight:
• There is zero upward vertical component, since the object moves entirely horizontally at this
point.
• There is still a fixed horizontal component, which is the same as at the start.
Near the e………… of the flight:
• There is a large downward vertical component, which is almost the same as the horizontal
component since the object is travelling at approx 45o to the horizontal downwards.
• There is still a fixed horizontal component, which is the same as at the start.
The flight path of a shot putt
Components of velocity during flight
Near the start of the flight:
• There is a large upward vertical component.
• But a fixed horizontal component.
At the middle of the flight:
• There is zero upward vertical component, since the object moves entirely horizontally at this
point.
• There is still a fixed horizontal component, which is the same as at the start.
Near the end of the flight:
• There is a large downward vertical component, which is almost the same as the horizontal
component since the object is travelling at approx 45o to the horizontal downwards.
• There is still a fixed horizontal component, which is the same as at the start.
QUESTION
1. Sketch a diagram to show the flight path of a shot putt from the moment it leaves the
putter’s hand to the moment it lands.
• Add arrows to the sketched flight path to represent the horizontal and vertical
components of the shot at the following points (Longer arrows mean greater force)
a) As it leaves the shot putter’s hand
b) The highest point of the flight path
c) the point of the flight path that is level to release
d) The point just before landing
2. How does the angle of release, height of release and velocity of release affect the
horizontal distance travelled by the shot putt.
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ANSWER
2. How does the angle of release, height of
release and
velocity of release affect the
.
horizontal distance travelled by the shot putt.
Generally an increase in velocity and height of
release will increase the horizontal distance
travelled by a shot putt. Because release
height is greater than landing height the
optimal release angle should be < 45degrees
Practice questions
3) Tennis players have to change direction quickly during a match to recover to the centre of the
court.
a) Draw a pin diagram of the tennis player as he pushes off the court surface to recover to the
centre of the court, showing all forces acting on the tennis player at this point. All forces must
be clearly identified.
3 marks
b) Explain the factors that affect the horizontal force at this point. Apply Newton’s second law of
motion to explain the effect of this force on the player.
•
horizontal forces, friction & air resistance
•
vertical forces, weight & reaction force
4 marks
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3) Tennis players have to change direction quickly during a match to recover
to the centre of the court.
a) Draw a pin diagram of the tennis player as he pushes off the court surface
to recover to the centre of the court, showing all forces acting on the
tennis player at this point. All forces must be clearly identified.
3 marks
• Weight force (m x g) (downwards)
• Reaction force (act at right angles to the contact surface) (upwards)
• Friction force (opposes motion) tennis player pushes down and backwards
on the ground, ground pushes up and forwards on the tennis player
b) Explain the factors that affect the horizontal force at this point. Apply
Newton’s second law of motion to explain the effect of this force on the
player.
• horizontal forces, friction & air resistance - for the tennis player to accelerate
he must use greater force against the playing surface, if there is grip
between the two surfaces this will increase friction and allow for greater
force to be applied.
•
vertical forces, weight & reaction force
4) a) A sprinter uses her calf muscles to push on the blocks at the start of a run. Explain, using Newton’s Laws,
how this enables her to accelerate forwards out of the blocks.
b) If the resultant forward force was 300 Newton and the runner’s mass was 60 kg, what would be her acceleration?
5) Explain the nature of the reaction force which provides forwards impulsion for a cyclist.
4 marks
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6) a) Using examples, explain how the shape of an object can alter its flight path. (air resistance)
4 marks
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b) Briefly explain why the flight path of a shot in athletics is so different from the flight of a badminton shuttle.
4 marks
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7) a) Identify three physical factors (not skill factors) which govern a swimmer’s speed and explain how one of
these occurs.
3 marks
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b) Give three examples, each from a different sporting context, to show how fluid friction affects the sports
person. Fluid friction (or drag) is a term applying to objects moving through fluids (gases or liquids). The force acts in the opposite direction to
the direction of motion. Fluid friction force depends on the shape and size of the moving object, the speed of the moving object, and the
streamlining effect
3 marks
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8. Show graphs of the forces acting on a runner’s foot during a 100m sprint.
For each graph, describe the resultant impulse force and the motion that occurs. 6 marks
a) Out of the blocks (+much > -)
b)Accelerating body (+> -)
c) Constant velocity (+ = - )
d) Decelerating body(+ < - )
9. Table 7.1 shows the speed of a 19 year-old male sprinter during a 200 m race.
a) Plot a graph of speed against time during this race. When does he reach maximum speed and what happens
to his speed between 8 and 22 seconds?
7 marks
b) Use the graph to establish his speed at 0.5 seconds and 1.5 seconds and calculate the average acceleration
between 0.5 and 1.5 seconds.
3 marks
Table 7.1 – data for a 200 metres sprint
Speed m/s
0.0
6.0
7.5
8.2
8.4
8.5
8.5
8.4
8.3
8.2
8.1
8.0
Time (s)
0
1
2
3
4
5
7
8
10
13
18
22
10) Successful games players are often able to change their velocity rapidly in
the game situation. Explain the biomechanics behind this ability using
examples from a game of your choice.
6 marks
Use the following terms (define velocity, force, acceleration,
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ANSWERS
2. How does the angle of release, height of release and velocity of release affect the horizontal distance
travelled by the shot putt.
Generally an increase in velocity and height of release will increase the horizontal distance travelled by a shot
putt. Because release height is greater than landing height the optimal release angle should be <
45degrees.
3) Tennis players have to change direction quickly during a match to recover to the centre of the court.
a) Draw a pin diagram of the tennis player as he pushes off the court surface to recover to the centre of the
court, showing all forces acting on the tennis player at this point. All forces must be clearly identified.
3 marks
•
Weight force (m x g) (downwards)
•
Reaction force (act at right angles to the contact surface) (upwards)
•
Friction force (opposes motion) tennis player pushes down and backwards on the ground, ground pushes
up and forwards on the tennis player
b) Explain the factors that affect the horizontal force at this point. Apply Newton’s second law of motion to
explain the effect of this force on the player.
•
horizontal forces, friction & air resistance - for the tennis player to accelerate he must use greater force against
the playing surface, if there is grip between the two surfaces this will increase friction and allow for
greater force to be applied.
•
vertical forces, weight & reaction force
4) a) A sprinter uses her calf muscles to push on the blocks at the start of a run. Explain,
using Newton’s Laws, how this enables her to accelerate forwards out of the blocks.
• 1st Law - The sprinter uses her calf muscles to produce a muscular force which is applied
to the blocks this will cause her velocity to change from rest to movement.
• 2nd Law - the greater the muscular force applied the greater the changes in the
acceleration of the sprinter.
• 3rd Law - The sprinter uses her calf muscles to push against the track this produces a
reactional force which is equal and opposite which will cause the sprinter to decelerate
and eventually stop.
b) If the resultant forward force was 300 Newtons and the runner’s mass was 60 kg, what would
be her acceleration?
Force = Mass x Acceleration 300 = 60 x a
a = 5m/s squared
5) Explain the nature of the reaction force which provides forwards impulsion for a cyclist. 4 marks
•
•
Impulse is the length of time a force is applied to an object/body that changes its momentum.
When one object pushes on another, the first object experiences a force equal but opposite in direction to
the second
•
in cycling, the tyre on the rear wheel pushes backward on the ground, the ground then
pushes forward on the rear wheel in an equal but opposite direction giving a forward
impulse.
6) a) Using examples, explain how the shape of an object can alter its flight path.
4 marks
Once in the air projectiles are only subject to the forces of gravity & air resistance which can
effect its normal flight path
• If weight were the only force acting, the flight path would be parabolic in shape, (shot or
hammer, the human body in jumps or tumbles or dives). Air resistance has minimal effect on
these objects
• For other objects such as a shuttlecock or table tennis ball the effect of air resistance is
greater causing the projectile to veer away from the normal parabolic path.
The shape & weight of a shuttlecock allows air resistance to effect its flight path veering it away
from the normal parobolic path.
A shot putt’s weight is heavy and airodynamic (smooth) therefore is not effected by air resistance
but is affected by gravity this will give it a parabolic flight path
The shape of a rugby ball is airodynamic streamline which when passed correctly (spun) will pass
through the air easily and its flight path will not be easily effected by air resistance.
b) Briefly explain why the flight path of a shot in athletics is so different from the flight of a
badminton shuttle. 4 marks
The flight path of an object can be effected by gravity or air resistance
The flight path of a shot putt is parobalic because its weight does not allow it to be effected by air
resistance. The flight path of a shuttlecock is distorted non parobalic because the shuttle’s
shape and weight allow it to be affected by air resistance.
7) a) Identify three physical factors (not skill factors) which govern a swimmer’s speed and explain
how one of these occurs.
fluid friction
High values of friction will occur for any sportsperson moving through water, and hence fluid
friction is the critical factor governing swimming speed.
The swimmers body shape is adjusted to minimise fluid friction.
The swimming hat is designed to minimise turbulent flow.
The swimsuit is designed to assist streamlining.
Cross sectional area is the area of the moving object as viewed from the front. The smaller
the better to reduce drag, hence swimmers enter the hands into the water close together
and keep elbows in!