Transcript Force summation

You will learn the following
• Stability & Balance
• 1) centre of gravity
• 2) line of gravity
• 3) base of support
• Newton’s 3 laws of motion
• 1st Law of Inertia
• 2nd Law of Acceleration
• 3rd Law of Action/reaction
• Force summation
• Levers
• Projectile motion
Stability & Balance
• Maintaining stability and _________ during sporting
situations/performance has a number of benefits. It
allows a person to put more force into a movement and
complete that movement ____________ and with
control. Achieving balance and stability involves
______________ your centre of gravity, line of gravity
and base of _________.
• Support Accurately Balance
controlling
Stability is defined as:
The ability to hold or maintain a position in space
Answers
• Maintaining stability and balance during sporting
situations/performance has a number of benefits.
It allows a person to put more force into a
movement and complete that movement
accurately and with control. Achieving balance
and stability involves controlling your centre of
gravity, line of gravity and base of support.
• Principle 1
the closer the line of gravity is to the centre of the
base of support, the greater the probability of
maintaining balance
• Principle 2
the broader the base of support, the greater the
probability of maintaining balance
• Principle 3
the probability of maintaining balance increases
when the COG is lowered in relation to the BOS
Principle 4
the further one body part moves away form the line
of gravity, the probability of maintaining balance
decreases unless another body part moves to
compensate for it.
Principles of stability and balance
• Principle 1
the closer the line of
gravity is to the centre
of the base of
support, the greater
the probability of
maintaining balance
Line of gravity
Principles of stability and balance
• Principle 2
the broader the
base of support,
the greater the
probability of
maintaining
balance
Base of support
Principles of stability and balance
• Principle 3
the probability of
maintaining balance
increases when the
COG is lowered in
relation to the BOS
Bending his knees
to be more balance
Principles of stability and balance
• Principle 4
the further one
body part moves
away form the line
of gravity, the
probability of
maintaining balance
decreases unless
another body part
moves to
compensate for it.
Stability and Balance
• There are three concepts of
stability and balance…
• 1) Centre of gravity (COG)
• 2) Line of gravity (LOG)
• 3) Base of support (BOS)
Centre of Gravity
• The point at which all parts of the body/object
are equally balanced
Determining the Centre of Gravity
Box Method
Where you draw a box around the object and
draw diagonal lines in the shape of an X inside
the box, the point at which the two lines cross
is the COG.
• When we stand in the anatomical
position, our COG is located around the
hip region.
Line of Gravity
• Is the vertical line that passes through the
centre of gravity to the ground. This line can
fall outside of the body if it is on an angle.
Base of Support
• The area within an object’s point of contact
with the ground. The larger the area the base
of support covers, the more stable an object
will be. The persons feet are normally their
BOS.
• BOS is the area within an objects point of contact with the ground. The
larger the area the base of support covers, the more stable an object will
be.
Wide BOS
Narrow BOS
BOS
BOS
Base of support – The object on the left is more stable
because of its relatively larger BOS
• The picture on the left has a ________Base of
support and therefore is more balanced than
the picture on the right. The picture on the
right has a small _________________ as her
feet are close together, which means she has
less balance than the picture on the left.
Line of gravity
Line of gravity
Centre of
gravity
Centre of
gravity
STABLE
UNSTABLE
Line of gravity
Increasing stability and balance
• To increase the stability and balance of a
person you can do the following things
• Widen the base of support by putting feet
shoulder width apart and having as many
body parts in contact with the ground at
once.
• Lowering the centre of gravity by bending
knees (to get closer to the ground)
What other factors can increase
stability?
• 1) Increase friction with the playing surface egspikes or sprigs on boots
• 2) Lean into an oncoming force eg- leaning into an
oncoming tackle in rugby or league
• 3) Increase rotation eg- you are more stable on a
bike moving than one standing still
• 4) Increase mass eg- a larger person is harder to
move because they have more inertia
REVISION
• 1) Which item on my foot with give me the biggest
Base of Support (BOS) and Why?
• Ice skates
Rugby boots
Flippers/Fins
canvas shoes
Sports shoes
• 2) Which item from the list above would give me
the smallest Base of Support (BOS) and why?
• 3) Define Centre of Gravity (COG)
• 6) If i want to lower my COG what can i do?
Define the following terms
• Define the following terms
• 1) BOS• 2) LOG• 3) COG-
Can you apply the principles of
balance to a rugby player about to be
tackled.
How can we make the following
situations more stable?
Applying the Theory of Balance
Why does
this not
fall over?
Because LOG falls inside the base of
support
Sporting Examples for each
•
•
•
•
Principle 1
Principle 2
Principle 3
Principle 4
Who is more balanced? Why?
How do these people remain
balanced?
Newton’s Laws
• Newton’s First Law – Inertia
• Newton’s Second Law – Acceleration
• Newton’s Third Law – Action/Reaction
Newton’s First Law
Newton’s 1st Law of Inertia
• An object at rest
tends to remain at
rest unless acted
upon by some
external force.
• What’s the
external force?
Newton’s 1st Law of Inertia
• That means that if an object is moving, it
tends to keep going unless something
stops it, like friction or gravity or this guy.
Newton’s 1st Law of Inertia
• It also means that an object that is not
moving stays put unless something hits it,
pushes it, or pulls it.
Question
•How does Newton's 1st
law apply to a basketball
jump shot?
Newton’s 2nd Law
Newton’s 2nd Law of
Acceleration
• Newton’s Second Law – Acceleration
When a force acts upon a
mass, the result is
acceleration of that mass
(F = m x a)
Newton’s 2nd Law of
Acceleration
*The harder you hit the ball, the faster
and possibly further it will travel.
*Or the softer you hit the ball, the
slower and less further it will travel.
*The mass will accelerate in the
direction the force is applied
Question
•How does Newton's 2nd
law apply to a basketball
jump shot?
Newton’s 3rd Law
Newton’s 3rd Law
For every action,
there is an equal
and opposite
reaction.
Newton’s 3rd Law
Question
•How does Newton's 3rd
law apply to a basketball
jump shot?
Summary
• 1st Law – the ball will remain at rest
until a force is applied to it.
• 2nd Law – the greater the force
applied, the greater the acceleration
of the ball.
rd
• 3 Law – the runner applies an action
force on the ground and the ground
applies a reaction force back.
FORCE
SUMMATION
Force Summation
• To give an object momentum in
activities such as throwing, kicking or
striking an object, the amount of
momentum given to the object is
determined by ‘the sum of all forces
generated by each body part’ (i.e.
Force summation).
Force Summation
• To gain maximum momentum, the force
needs to be generated by:
1. Using as many segments of the body
as possible.
2. In the correct sequence, using large
muscles first and then the smallest
muscles last but fastest.
3. With correct timing.
4. Through the greatest range of motion.
To achieve maximum force in the “Block” in the
game of basketball the athlete needs to lead with
there ____________ then this follows through to
their ____________/___________ and finally
with the _____________ as they extend up to
block the ball coming onto their side of the court.
• Arms
Legs
Trunk/back
If you wanted to shoot a 3 pointer in
basketball, list the order of muscles (by group,
not by individual muscles) that would be used
in order to play this shot with correct force
summation
1
________
_________
_______
________
_________
_______
Lower arm, shoulder, lower legs, back/trunk,
upper arm, upper legs
Highlight which answer is correct
below…
• A) force summation is the process of using
smaller muscles to bigger muscles in the
correct timing order to create the greatest
force
• B) force summation is the process of using
bigger muscles to smaller muscles in the
correct timing order to create the greatest
force
Answer
• B) force summation is the process of using
bigger muscles to smaller muscles in the
correct timing order to create the greatest
force
FORCE SUMMATION LAB
• Complete force summation lab in 4’s-5’s.
Equipment
• measuring tape/ and ball
Task
Throw the ball sitting down
Throw the ball standing up
Throw the ball using a step and throw
Question?
• To achieve maximum power in a punch the
legs and the trunk leads the movement.
Explain why?
Question?
• E.g. the bigger stronger muscles of the upper
body/trunk initiate the movement followed by
the muscles of the upper arm and finally the
lower arm. To gain maximum force in the cross
punch all muscles will be used. The muscles
need to be used sequentially. The entire
movement must be completed over a stable
base as this will ensure maximum force.
SUMMARY
• To gain maximum momentum, the force
needs to be generated by:
• Using as many body parts as possible.
• In the correct sequence (use large
muscles first & then the smallest muscles
last but fastest).
• With the correct timing.
• Though the greatest range of motion.
REVISION
What does this relate to.....
Revision Questions
• Fill in the blanks with the words down
the bottom....
• The more ---- ------- involved, the
greater the force or ----- generated.
(eg. A shot-putter should use the legs,
hips, ----, shoulders, arms, and ----- in
order for maximum distance.
• speed, wrist, back, body segments
Revision Questions
• The more body segments involved, the
greater the force or speed generated. (eg.
A shot-putter should use the legs, hips,
back, shoulders, arms, and wrist in
order for maximum distance.
Revision Questions
Fill in the blanks with the words on the bottom...
To gain maximum --------, the force needs to be
generated by:
• Using as many ---- parts as possible.
• In the correct sequence (use ------ muscles first &
then the -------- muscles last but fastest).
• With the ----- timing.
• Though the greatest range of --------.
• momentum, large, body, smallest, correct, motion
Revision Questions
To gain maximum momentum, the force
needs to be generated by:
• Using as many body parts as possible.
• In the correct sequence (use large muscles
first & then the smallest muscles last but
fastest).
• With the correct timing.
• Though the greatest range of motion.
Revision Questions
• To achieve
maximum
power in a set,
the legs leads
the movement.
Explain why?
Force of Summation
• The bigger stronger muscles of the lower body
in the legs eg- hamstrings and quadriceps
initiate the movement followed by the
muscles of the trunk/back then the upper arm
and finally the lower arm. To gain maximum
force in the set all muscles should be used,
The muscles need to be used sequentially. The
entire movement must be completed over a
stable base as this will ensure maximum force,
i.e. both feet on the ground.
List the order of joints then muscles
used for force summation
knee, wrist, back/trunk, ankle, , shoulder, elbow, hip,
Revision
• Come up with sporting examples
that could be used for each of
Newton’s Laws...
• Three sporting examples for
each...
Projectile Motion
What is projectile?
• Projectile -As soon as an object is thrown it
becomes a projectile.
What is Projectile Motion?
• Projectile motion is the curved path that an
object follows when thrown, or launched
Yes Examples
•
•
•
•
•
•
•
Tennis ball
Football
Golf ball
Basketball
Javelin
Jumping out of a car
Cannon ball
Non Examples
• Plane
• Rocket
• Missile
An object moving in projectile
motion has two components:
• Horizontal
• Vertical
Consider a pitcher throwing a baseball:
a) After the ball leaves the pitcher’s hand, the ball’s
horizontal velocity is constant.
b) The ball’s vertical
velocity
increases because
gravity causes
it to accelerate
downward.
c) The two motions
combine to form a
curved path.
How to throw an object further...
•
•
•
•
Change the...
Height of release (the higher the better).
Speed of release (the faster the better).
Angle of release (45° for optimum
distance).
Factors Affecting Projectile Motion
• Speed of Release
Generally, the greater the speed of release,
the greater the distance gained.
Initial Vertical
Velocity
Direction of Flight
Initial Horizontal Velocity
Factors Affecting Projectile Motion
• Angle of Release
In sporting situations the angle of release is
usually always lower, around 35° to 45°.
Factors Affecting Projectile Motion
• Height of Release
The greater the height of release the greater the
distance gained, why?
Time in the air will be greater.
Would this mean that Mr Rameka (The Great)
could throw a ball at the top of a hill would hit it
further than at the bottom of the hill? Why?
Yes the ball will stay in the air longer so will have a
greater chance to fly further. This assumes the
same club and force is used.
Height of release
Levers
What are levers?
• Mechanical devices.
• Help with movement about a fixed axis.
Functions of levers…
• Help muscles
to move larger
weights.
• Increase the
speed that a
body can
move at.
Levers in the human body
•
•
•
•
Bones = levers.
Joints = fixed axis - FULCRUM
Muscles = move levers - EFFORT
Limb/weight = anything heavy-LOAD
The
3 Types of lever
• First Class Lever
• Second Class Lever
• Third Class Lever
• Each is classified by the relationship between
the Fulcrum (F), Load (L) and Effort (E).
First Class Lever
• Fulcrum lies in the middle of the effort &
load…
Effort
Load
Examples of first class levers…
• Nodding
your
head.
First class levers in sport…
How do 1st class levers help us to
move?
• Help joints to move quickly – e.g. the javelin
throw.
• AND
• Helps with moving heavy weights – e.g. whilst
rowing.
Second class lever
• Load lies in the middle of the fulcrum &
effort…
Load
Fulcrum
Effort
Examples of a second class lever…
• Standing
on tiptoe.
Second class levers in sport…
How do 2nd class levers help us to
move?
• Generates
large
amounts of
force
(Strength).
Third class levers
• Effort lies in between the fulcrum and the
load…
Effort
Load
Examples of a third class lever…
• Bicep curl.
Examples of 3rd class levers in sport…
How do 3rd class levers help us to
move?
• Most common type of
lever in the human body.
• Helps to increase the
speed of movement.
Why 3rd class levers are the most
useful…
• Move loads a large distance with only a small
movement of the effort arm.
• A wide range of movements are possible.
• Increases speed of the body/lever system.
• BUT – only light loads can be moved.
• Due to the shortness of the effort arm.
An easy way of remembering…
Mechanical Advantage…
• How efficient a lever system is.
• i.e. when a lever system puts out more force
than it puts in.
• Depends upon the lengths of the resistance
(load) & effort arms…
Effort Arm…
• Part of the lever between F & E.
• Long effort arm = less effort needed to move a force.
• The ball of your foot.
• MECHANICAL ADVANTAGE
Resistance Arm…
• Part of the lever between F & L.
• Long resistance arm = great speed.
• E.g. Lacrosse
• MECHANICAL DISADVANTAGE
REVISION
Summation of Forces
•
1.
2.
3.
4.
5.
In a tennis serve, describe what muscles are
used and in what order they are recruited?
Core
Hips
Deltiods
Shoulder
Wrist/Hand muscles
•
The force used to hit the ball is a combination of
all the individual muscle firing in sequence.
•
For your own sport choose a specific skill and list
the order of muscles that are recruited.
Principle #1
• What happens as we
move the line of
gravity closer to the
edges of the base of
support?
We become more unstable and the chances of
losing balance increases, when we move the line
of gravity closer to the edges of the BOS.
Questions
Write down 5 sporting examples of Inertia
1.
2.
3.
4.
5.
A stationary soccer ball resting on the pitch
.
.
.
.
Mix and match
Action/ Reaction
Inertia
An object at rest
For every action
tends to remain
there is an equal
at rest until
and opposite
acted upon by an
reaction
external force
3rd law
1st law
Acceleration
When a force
acts upon a
mass, the result
is acceleration of
that mass
2nd law
Using the photos below and your knowledge of
force summation, explain how force is applied in
a volleyball serve.
Revision
• Come up with sporting examples
that could be used for each of
Newton’s Laws...
• Three sporting examples for
each...
Revision
st
1
Law – Soccer free kick, hitting a
golf ball, rugby conversion
nd
2 Law – Golf/cricket/tennis –
swinging a club slowly with force
gives the ball less momentum
3rd Law – running, dribbling a
basketball, jumping
So, the law is as follows:
Soft action - __________ reaction
Hard action - __________ reaction
Which of the following is the MOST
STABLE?
B
A
C
A is the most stable because:
•They have the lowest centre of gravity
•They have the largest base of support
•And like C their centre of gravity is in the centre of the
base of support
X
X
X
The LARGER the area of your Base of
Support, the MORE STABLE you will be
Match each statement with the correct
Law..... Without looking at your notes.
• The runner applies an action
st
1 Law force on the ground and the
ground applies a reaction
force
back.
nd
2
• The ball will remain at rest
Law
until a force is applied to it.
• The greater the force
applied,
the
greater
the
rd
3 Law acceleration of the ball.
Which Law is this?
The Tennis Serve – done correctly!
• http://www.youtube.c
om/watch?v=n76f2KJ3
6yA
The Tennis Serve – done incorrectly!
• http://www.youtube.com/w
atch#!v=2kpelRORbGk&feat
ure=related
• http://www.youtube.com/w
atch#!v=CFrdOjgy7Bo&featu
re=related