Sport Science Levers, laws of motion

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Page 2: Overview of Levers

• Introduction to Levers

  • A lever is a simple machine that consists of a rigid rod that rotates around a fulcrum when a force is applied.

  • The ability to generate movement depends on:

    • Magnitude of forces involved

    • Distance between the fulcrum and the line of action of the force.

• Role of Bones

  • Bones act as levers when muscles contract.

• Types of Levers

  • There are three types of levers both within and outside the human body.

• Mechanical Advantage (MA)

  • Assess efficiency of a lever.

  • Equation: MA = (magnitude of load force) / (magnitude of effort force).

  • Effort Arm vs. Load Arm

    • The length differences between the effort arm and load arm affect mechanical advantage.

Page 3: Types of Levers

• First-Class Levers

  • Effort and load forces are on opposite sides of the fulcrum.

  • Rare in human body; e.g., holding the head up.

• Second-Class Levers

  • Effort and load forces are on the same side of the fulcrum.

  • Effort arm is longer than load arm.

  • Rare in human body.

• Third-Class Levers

  • Effort and load forces are on the same side of the fulcrum.

  • Effort arm is shorter than load arm.

  • Mechanical advantage is always less than 1; less efficient at generating motion but produces greater angular movement.

• Application in the Human Body

  • Third-class levers are the most common. Tendons attach close to joints, resulting in shorter effort arms.

• Examples of Levers

  • Inside the body: throwing a ball (fulcrum is the shoulder, effort from contracting muscles).

  • Outside the body: various sports equipment like bats and poles.

Page 4: Collision Experiment

• Experiment Overview

  • A ruler was taped to the wall, marking the drop point of a ball to observe collisions using video analysis (Logger Pro).

• Data Collection

  • Conducted four trials to find the coefficient of restitution.

• Human Error Consideration

  • Discussed potential sources of error and improvements.

• Friction

  • Defined as a force resisting sliding motion between surfaces. Directs parallel to contact surfaces.

  • Walking mechanics: Feet push backward on ground; friction prevents sliding.

Page 5: Types of Friction

• Static Friction

  • Acts when objects remain stationary relative to each other, preventing movement.

  • Coefficient of Static Friction: Ranges from 0 to 1; more interaction yields higher values.

• Dynamic Friction

  • Acts when objects slide past each other and is generally lower than static friction.

• Impact on Sports Performance

  • High friction improves traction (e.g., shoes, sports equipment).

  • Low friction can hinder performance in certain activities.

Page 6: Kinematics

• Definition

  • Kinematics is the study of motion, focusing on changes in position.

  • Types of motion:

    • Linear (straight)

    • Curvilinear (curve)

    • Angular (around an axis)

• Scalars vs. Vectors

  • Vectors possess both size and direction (e.g., velocity, force).

  • Scalars only have size (e.g., speed, distance).

• Position Measurements

  • Typically captured in coordinates relative to an origin in 2D or 3D.

Page 7: Linear Kinematics

• Displacement

  • Defined as the change from the origin; represented as S.

  • Distance is linear, represented as d.

• Velocity

  • Rate of change in position; calculated as V = (difference in position) / (difference in time).

  • Units: m/s.

• Acceleration

  • Change in speed, direction, or both.

  • Positive if speeding up; negative for slowing down.

Page 8: Angular Kinematics

• Angular Motion

  • Movement around an axis with angular displacement measured in degrees or radians.

• Angular Velocity

  • Change in angular position over time, represented by 'ω'.

• Angular Acceleration

  • Change in angular velocity divided by time; represented by 'α'.

Page 9: Kinetics

• Force

  • Defined as a push or pull, manifested through contact or at a distance.

• Newton's Laws of Motion

  • First Law: Objects remain at rest or constant velocity unless acted on by an unbalanced force.

  • Second Law: F = ma (Force equals mass times acceleration).

  • Third Law: For every action, there is an equal and opposite reaction.

• Mass vs. Weight

  • Mass is the amount of material; weight is the force due to gravity, calculated as Fg = mg.

Page 10: Work and Power

• Definition of Work

  • Transfer of energy through force applied over distance.

• Power

  • Measure of how quickly work is done; critical for performance in sports.

  • Key for optimizing sports techniques and equipment.

Page 11: Principles of Stability

• Factors Affecting Stability

  • Larger mass leads to greater stability.

  • A larger base of support increases stability.

  • A lower center of mass enhances stability.

  • The position of the line of gravity relative to the base of support affects stability.

Page 12: Forces in Sports Movement

• Combining Forces in Movements

  • Example: Jumping combines forces from muscles and ground. Excessive force can lead to injury.

• Linear Momentum and Impulse

  • Momentum equation: p = mv (momentum is mass times velocity).

  • Impulse involves the change in momentum, J = FΔt, indicating that the change depends on the force and duration of contact.

Page 13: Angular Movement

• Torque and Moment of Inertia

  • Torque involves a force applied around an axis; influenced by distance, size, and direction of force.

  • Moment of inertia reflects difficulty in rotating around an axis, affected by mass distribution.

• Angular Momentum

  • A potential measure of rotation influenced by the mass and distribution.

  • Conservation of angular momentum indicates an object maintains its momentum unless affected by external unbalanced forces.

Page 14: Body Segments and Angular Momentum

• Transfer of Angular Momentum

  • Each body segment's movement affects overall angular velocity, illustrating muscle use and segment interaction.

Page 15: Skeletal System Overview

• Skeletal Composition

  • Axial Skeleton: 80 bones including skull and vertebrae for protection and posture.

  • Appendicular Skeleton: 126 bones associated with limb movement.

• Anatomical Terminology

  • Defined terms include inferior, superior, proximal, distal, etc.

Page 16: Anthropometry and Ergonomics in Sports

• Importance of Anthropometric Data

  • Used for designing equipment to fit diverse body sizes, enhance comfort, and reduce injury risk.

• Ergonomic Design

  • Focuses on reducing discomfort and improving performance; includes optimizing equipment for better body alignment and minimizing joint strain.

Page 17: Joint Movements

• Fundamental Movements

  • Flexion, extension, abduction, adduction, rotation, etc.

  • Joint-specific movements like elevation, depression, pronation, and supination are critical for specific functionalities.