EXSS2020
Biomechanics
LABORATORY – WEEK 3
Practical Skills – Quantitative 2D Kinematic & Kinetic Analysis
Topic – Newton’s Law during Movement
Purpose
1. Consolidate your understanding of theoretical concepts and practical
implications of Newtons Law during movement, how it influences
movement technique and it’s for value for exercise prescription
2. Practice the process of quantitative analysis of human movement to
critique human motion.
3. Continue your practical skills learning of undertaking a two-dimensional
quantitative kinematic analysis
4. Further develop your capability to identify key assess errors in movement
performance and interpret their implication to develop and implement
intervention strategies relevant to the movement context
5. Apply the kinetic concepts of Newtons Laws to human motion to solve
mechanical problems in of movements performed in sport and
rehabilitation.
Course
Learning
Outcomes
1. Explain what biomechanics is and how it can be used to analyse human
movement;
2. Quantify the kinematics and kinetics of human movement using the
mathematics of mechanics (ESSA 2.2.1);
3. Identify and describe how mechanical principles affect and direct
performance and injury prevention in human movement and sport (ESSA
2.2.1, 2.2.2; 2.2.6);
4. Apply the processes of qualitative and quantitative movement analysis to
identify specific aspects of movement patterns important for
performance improvement and injury reduction (ESSA 2.2.3; 2.2.4; 2.2.5,
2.2.6)
ESSA Gradate
Outcomes
2.2.1. Describe biomechanical principles and how they relate specifically to
the analysis of various forms of human movement to demonstrate an
understanding of:
2.2.1.1. Movement analysis knowledge and skills.
2.2.1.2. Scientific approaches to ascertaining the aetiology of injury
and acute, chronic and complex conditions as they relate to
movement.
2.2.1.3. The physical effects of human interaction with equipment and the
environment.
2.2.2. Apply the principles of the biomechanical analysis of human
movement to activities of daily living across a broad range of
populations.
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Biomechanics
2.2.3. Analyse biomechanical problems and develop and implement relevant
intervention strategies to the movement context.
2.2.4. Choose and interpret biomechanical measurements relevant to
client’s needs.
2.2.5. Choose and apply appropriate communication to explain scientific
data and movement techniques to clients and other professionals.
2.2.6. Identify specific aspects of movement patterns important for
performance improvement and injury prevention.
Movement Analysis Multimedia Presentation (5 min video) – this laboratory
will continue to build your knowledge of qualitative movement analysis in
sport and exercise.
Relevant
Assessments
Practical Assessment – this laboratory continues your practical learning of
performing a qualitative analysis of human motion and how you communicate
this information to clients and other professionals.
Final Examination – these practical tasks within this laboratory will assist you
support your understanding application of identifying biomechanics principals
of movement.
Practical Skills
2D quantitative kinematic analysis: analysis of gait using SiliconCoach
software.
Quantitative kinetic analysis: calculating weight forces.
Recommended
Readings
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1. Blazevich AJ (2010). Sports Biomechanics The Basics: Optimising human
performance. (2nd ed.). A & C Black. Chapters 4.
EXSS2020
Biomechanics
Practical Skills – Quantitative 2D Kinematic & Kinetic Analysis
Topic – Newton’s Law during Movement
TASK 1: Newton’s First Law of Inertia - Linear
INTRODUCTION
A body will maintain a state of rest or constant velocity unless acted on by an external force that
changes the state is called Newton’s Law of Inertia.
EQUIPMENT
Tug-a-war rope, scale.
PROCEDURE
1. Form two teams of four people.
Stand on the digital scales and record the mass of each individual in
2. Table .
Now calculate the weight in
3. Table .
Calculate the weight of each team in
4. Table .
Table 1
Individual
1
2
3
4
Tug-A-War team weights.
Mass (kg)
75kg
81kg
57kg
82kg/84kg/70kg
Weight (N)
735.75N
794.61N
559.17N
Team Weight (N)
Team A
213kg or 2130 N
Team B
236kg or 2360N
Question: Based on your calculation of team weight, which team will most likely win? Explain your
answer?
Team B due to more mass and the force direction being pulled will be stronger than team A.
5. Each team is to hold onto one end of the rope with the middle of the rope over a line on the
ground. On the instructions of the start, both teams will commence a tug-a-war. The team that
wins is the one who pulls one team member of the other team across the line.
Question: Was your prediction of which team would win based on team weight correct? If not, explain
your answer. (We will revisit these other explanations later when learning the concepts of stability).
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Biomechanics
Yes
TASK 2: Newton’s Second Law of Acceleration - Mass and Weight
INTRODUCTION
The weight of an object is defined as the force of gravity on the object and may be calculated as the
mass times the acceleration of gravity, w = mass x gravity (F = ma). This is Newtons’ Law of Acceleration
Since the weight is a force, its SI unit is the Newton (N). Weight will vary according to the accelerations
the body is experiencing.
EQUIPMENT
Lift, analogue scale.
PROCEDURE
1.
2.
3.
4.
5.
6.
Stand on the analogue scales and record your mass = 75 kg.
Now calculate your weight = __750__ N.
Walk to a lift in a building.
With ONLY you in the lift stand on the scales and take note of your weight.
Now press the lift UP button while looking at the weight scales.
Repeat but now press the DOWN lift button.
Question: What happened to your weight when you went up or down in the lift? Did your weight
increase, decrease or remain unchanged? Why did this happen (remember weight is a force equal to
mass multiplied by acceleration)?
Weight decreased when you move up the elevator, and increased when you move down the elevator.
This is because the acceleration by gravity is applied down on the person, increasing the overall
weight.
Question: What is the difference between mass and weight? Why when talking about a person’s
“weight”, it is the incorrect term to use?
Mass is in kg and weight is in N. Weight is mass times acceleration. Weight can change due to the
acceleration but mass stays the same.
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Biomechanics
TASK 3: Free body diagrams and force vector resolution
EQUIPMENT
Scales, calculator and weight.
PROCEDURE
1. Select a person to hold a small weight in their hand with the elbow held at 90°. Using the
information below, draw a free body diagram depicting all the forces acting on the forearm
segment in Figure .
2. Use vectors to represent the various forces acting on the free body diagram.
3. Use the concept of the sum of the forces is equal to zero to calculate the force required by the
biceps tendon in order to hold the forearm in a fixed (static) position. ∑F = 0
4. Calculate the mass and weight of the segments in Table 2
Figure 1
Table 2
Segment
Free body diagram of the forearm segment
Upper extremity masses and weights.
Male (% of BW)
Female (% of BW)
Mass (kg)
Upper Arm
3.25
2.90
1.74kg
Forearm
1.87
1.57
0.942kg
Hand
0.65
0.50
0.3kg
*Segments weights are expressed in percentage of total body weight.
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Weight (N)
17N
9.24N
2.943N
EXSS2020
Biomechanics
Free body diagram
Force needed to hold weight 31.683 N
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EXSS2020
Biomechanics
Task 4: Newtons Third Law of Action & Reaction - Angular application
INTRODUCTION
Newton’s Third Law of motion states that for every action (force exerted), there is an equal (in
magnitude) and opposite (in direction) reaction (force) exerted back on the first body. The angular
version of this law states that for every torque exerted, there is an equal torque exerted in the
opposite direction. Sports offer countless examples in which this concept of action and reaction is
applied. Perhaps the most common is that in which an athlete’s applies a torque to one part of their
body, thereby causing it to rotate. An equal and opposite reaction to this torque causes some other
part to the body to rotate in the opposite direction. For example, when a long jumper swings his legs
forward (and upward) reading for landing, the magnitude of this action is accentuated if a torque
equal and opposite to that exerted on the legs is applied to the remainder of the body.
EQUIPMENT
2kg dumbbells, soccer ball and tape measure.
PROCEDURES
1. Select a participant to perform a standing long jump using two different techniques:
i.
Instruct the participant to use their arms to generate forward and upward momentum
(not down and backward).
ii.
Instruct the participant to use their arms to generate backward and downward
momentum and then let go the dumbbells in the air.
2. Record the horizontal displacement of the standing long jump using the two (2) different
techniques in Table 2.
Table 2
Utilising angular action and reaction during a standing long jump.
Technique
Horizontal Displacement (m)
i
ii
Question: Explain why there was a difference in the horizontal displacement when utilising the two
different techniques.
The force generated by the downward and backward motion creates some extra force and potential
to leap backward. The force is acting against the drag. With the forward and upward motion, the
motion is going with the drag, therefore, the horizontal displacement is decreased. Technique plays a
huge role.
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Biomechanics
1. Instruct a participant to perform a jump to head a soccer ball.
2. Analyse the rotational action reaction effect of the movement by Identifying the:
i.
Body part initiating the action (The neck)
ii.
Body part responding to the action (Head and arms and torso)
iii.
hinge around which both body parts rotate (Head rotate the way of the ball and the legs
rotate the opposite direction.
1. In the space below draw a diagram of the action and reaction in this rotational movement.
2. In rotational motion the direction is specified as clockwise or anticlockwise with the movement
occurring in the same spatial pathway. Label the direction of the rotational motion in your diagram
below. (Head is anticlockwise and torso is clockwise).
Question: Describe how Newton’s principle of action and reaction is utilised when a soccer player
jumps to head a soccer ball?
Everything has an opposite and equal reaction. By generating enough power and force, the ball will
be moving further to even out the differences.
An example of the action and reaction principle is in the Long Jump Technique Utilising. When a long
jumper swings his legs forward and upward in preparation for landing, the quality of this action is
accentuated if a torque equal in magnitude and opposite in direction to that exerted on the legs is
applied to the reminder of the body. This is most commonly and effectively accomplished by rotating
the arms aggressively downward and backward. There are also many more examples in a wide variety
of sporting movements.
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EXSS2020
Biomechanics
Question: As a coach, you are teaching a basketball player to perform a jump shot. However, they are
having difficulty in executing this movement task whilst airborne. Explain using biomechanical
principles of how you would instruct the player to perform the movement.
Get them to move upward and keep the body straight.
When a performer is in contact with the ground and initiating an action force with the leg such as
kicking, quite significant reaction will be observed in the arm as there are no limitations on its
movement. However, if the tennis player anchors the front leg when performing a backhand drive
then only a very limited reaction in the leg will be observed.
Question: Using the principles of action and reaction, and the conservation of momentum compare
when an individual kicks a ball and plays a backhand in tennis?
Kickball with leg higher.
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Biomechanics
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The use of the action reaction effect can help the performer to increase efficiency in many ways.
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Biomechanics
Question: In the beam in gymnastics, how can the use of the action and reaction effect help the
performance? What implications does this principle have in teaching children how to balance on a
beam?
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