Biomechanics and Friction Quiz

Biomechanics

• Biomechanics is the study of mechanics related to the function and structure of biological systems, focusing on humans.
• It applies physics, laws of motion, and forces to understand human movement.

Two Major Areas of Biomechanics

Kinematics

• Describes the details of motion.
  • Time: Duration of movement
  • Displacement: Distance of movement
  • Velocity: Speed of movement
  • Acceleration: Rate of change in velocity
  • Spatial factors: How motion occurs in space

Kinetics

• Studies the forces that cause motion.
  • Ground reaction forces: Forces exerted by the ground (e.g., via force plates)

Biomechanics Labs and Motion Analysis

Motion Capture (Kinematics)

• Uses infrared reflective markers to track body segment movement in 3D space.
• Captures displacement, velocity, and acceleration data

Force Plates (Kinetics)

• Measures ground reaction forces in both vertical and horizontal planes.

Machines in Biomechanics

• Provide mechanical advantage.

Types of Machines in the Human Body

Levers

• Most common machine in the human body.
• Components: Force, Axis (fulcrum), and Resistance.
• Classes of Levers:
  • First-Class: Axis between force and resistance (e.g., seesaw, neck)
  • Second-Class: Resistance between axis and force (e.g., wheelbarrow, standing on toes)
  • Third-Class: Force between axis and resistance (e.g., bicep curl, rowing)

Wheel and Axles

• Alter force direction and provide leverage.

Pulleys

• Alter force direction for example muscle action over joints.

Action Steps for Study

• Draw labelled diagrams of levers.
• Familiarize yourself with examples in the body.
• Focus on relationships between force, axis, and resistance in each lever class.

Key Concepts

• Key features of a lever include the force, axis (fulcrum), and resistance, arranged in specific orders defining the lever class.
• Mechanical advantage is the ratio of the length of the force arm to the length of the resistance arm, helping determine force balance.
• Torque is the force multiplied by the distance from the axis (moment arm), causing rotational movement.

Classes of Levers

• First-Class Levers
  • Axis is positioned between force and resistance
  • Examples include Seesaws and Scissors
  • The purpose is balance, speed, or range of motion depending on its axis placement.
• Second-Class Levers
  • Resistance acts between axis and force.
  • A common example is wheelbarrows.
  • The primary purpose is force advantage to move a large resistance with a small force.
• Third-Class Levers
  • Force is positioned between the axis and resistance.
  • An example is rowing or shoveling
  • The lever's function is speed and range of motion at the expense of force.

Human Body Leverage System

• The human body is built for speed and range of motion, not force.
  • Force arms in the body are typically shorter than resistance arms.
  • Muscles need significant strength to move long resistance arms.

Pulleys

• Pulleys redirect force and potentially increase mechanical advantage in multi-pulley systems.

Motion and Force

• Movement requires force.

Internal Force

• Muscle contractions

External Force

• Interaction with external objects (e.g., collisions)

Motion

Linear Motion

• Movement in a straight line.

Angular Motion

• Rotational movement.

Relation Between Angular and Linear Motion

• Angular motion in joints generates linear motion (e.g., walking).
• Longer limbs or tools produce greater linear velocity during angular motion.

Examples of Angular and Linear Motion

• Windmill blades, golf clubs
• Tools or equipment

Newton's Laws of Motion

Law 1 (Inertia)

• A body in motion stays in motion, and a body at rest stays at rest, unless acted on by an external force
• Muscles create force to overcome inertia during movement.

Law 2 (Momentum and Impulse)

• Momentum = mass × velocity.
• Greater momentum resists change in motion.

Application of Impulse

- Kicking a ball changes the ball's momentum
- Catching a ball slows it down gradually
- Helmets reduce impulse during impacts.

Summary of Key Biomechanics Applications

• Angular motion often couples with linear motion in numerous applications.
• Newton's laws of motion explain motion dynamics and resistance.
• Biomechanics principles improve efficiency in sports and physical task performance, reducing injury risk.

Acceleration

• Defined as change in velocity (not speed).
  • Positive or negative: depending on direction of velocity change
• Acceleration equation: acceleration = Force/Mass
• Directly proportional to force applied and inversely proportional to mass.

Muscular Force

• High force is required to accelerate large masses of objects.

Newton's Third Law (Reaction)

• For every action, there is an equal and opposite reaction.
• Ground reaction force is the force exerted by the ground in response to force from the body (e.g., walking, running)

Friction in Motion

Definition

• Resistance between two surfaces in contact.

Types of Friction

• Static: Resistance before movement. Superior to kinetic friction.
• Kinetic: Resistance during movement.

Factors Affecting Friction

• Surface Texture: Rougher surface means more friction.
• Normal Force: Larger surface, or greater contact between the surfaces, means greater friction.

Coefficient of Friction

• Ratio of force required to overcome friction to the holding force of the surfaces together.

Rolling Friction

• Resistance of a rolling object (e.g., wheel, ball) on a surface. 
• Generally lower than static or kinetic friction.

Test your understanding of biomechanics and the concepts of friction in various scenarios. This quiz covers the relationship between static and kinetic friction, the effects of different surfaces on movement, and the principles of levers in biomechanics. Challenge your knowledge with various questions focusing on these key topics.