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## Biomechanics: Outline

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**Biomechanics: Outline**• Definition • Types of Motion • Measuring Motion • Describing the Geometry of Motion: Kinematics • Linear • Angular • Describing the Forces of Motion: Kinetics • Linear • Angular • Fluid Mechanics**Biomechanics**• The study of the structure and functions of biological systems by means of the methods of mechanics Hatze, 1974**Motion**• Kinematics • Kinetics**Types of motion**• Linear (translation) • all parts travel the same distance in the same time along the same path**Type of Motion**• Angular motion**General Motion**Most movements are likely a combination of both linear and angular motion**Kinematics**Kinetics Other Measuring Motion**Kinematics: Film Analysis**SETUP CALIBRATION ANALYSIS**What might we measure?**KINEMATICS: Spatial component • Position • Displacement • Distance**What might we measure?**• Center of gravity the point about which a body’s weight is equally balanced in all directions (Hall, 1995)**Kinematics: Film Analysis**CALIBRATION SETUP ANALYSIS (50,490) ( (10, 570)**What might we measure?**Kinematics: Spatial and temporal components • Speed • Velocity • Acceleration**What might we measure?**Kinetics • Inertia • Force**Motion, Force, and Sir Issac**• First Law (Inertia)**Motion, Force, and Sir Issac**• Second Law (Acceleration or F=ma) e.g.1, a soccer ball (of fixed mass) will experience greater acceleration when kicked with more force e.g.2, for kick (of given force) a lighter soccer ball will experience greater acceleration**Motion, Force, and Sir Issac**• Third Law (action-reaction)**Angular Motion**• When a force is not exerted along a line that passes through a body’s center of gravity ____________ the body will experience angular _________ motion**What might we measure?**• Angular displacement • Angular distance angular motion consider in degrees, revolutions, or radians 1 radian = 57.3 degrees 1 revolution = 360 degrees 1 revolution = 6.28 radians**What might we measure?**• Angular Velocity • Units? • Angular Acceleration • Units?**What might we measure?**Angular Kinetics • Torque • Moment of inertia**Moment of Interia: Relative**• Tuck • Pike • Full body rotating around center of mass • Full body rotating around a bar**Extended swing**• around bar • Extended swing • around central axis • Pike • Tuck Assuming: Σmd2 Where: M = mass d = distance from axis of rotation**Fluid Mechanics**• Drag • Lift**Drag**Fluid force that opposes ________________________________________________________________________________________________ Will depend on:**Forms of Drag**• Surface (hydrodynamic drag) • Profile (Form) • Wave**Surface Drag**Water particles attract other water particles and will increase with “roughness of skin”**Profile Drag**• Low pressure pocket forms • and “holds back” the • cyclist. As velocity doubles this • resistive force quadruples!!!! • Important factors:**Reducing Drag**• Frame designs • on bikes are often • “tear-shaped” to • reduce drag • Drafting within 1 m • can reduce drag • accounting for 6% of • energy cost (e.g., ducks flying)**Lift**Component of air resistance that ____________________________________________________________________ Lift Resultant Drag Air Flow**High velocity/Low Pressure**Low velocity/High Pressure Lift - common example How might you use this principle in Formula 1 racing?**Intended Direction**Flight Path Air Flow Low Pressure Magnus Effect • Force first discovered by Magnus. It explains the curving of a spinning ball. As the spinning object pushes the air from one side to the other, it will create a lower pressure zone, making the object move faster on one side.**Kinematics**linear motion displacement, velocity.. Angular Motion angular displacement… Kinetics linear motion mass, inertia Angular Motion torque, moment of inertia Review • Fluid dynamics • drag • lift