KIN 3309 1nd Edition Lecture 15 Outline of Last Lecture I. Angular KinematicsII. Types of AnglesIII. Calculating Absolute AnglesIV. Calculating Relative AnglesV. Angular Position, Distance, DisplacementVI. Angular Motion VectorsVII. Angular and Linear MotionVIII. Angular and Linear VelocityIX. Tangential VelocityX. Maximize Linear Velocity?XI. Tangential AccelerationXII. Centripetal (radial) AccelerationXIII. Angle-Angle DiagramsXIV. QuizOutline of Current Lecture I. OutlineII. Kinematics vs. KineticsIII. Sources of Forces Affecting Human MovementIV. ForceV. Composition and Resolution of ForcesVI. Newton’s Laws of MotionVII. Newton’s 1st Law: Law of InertiaVIII. Newton’s 2nd Law: Law of AccelerationIX. Newton’s 3rd Law: Law of Action-ReactionThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.X. MomentumXI. Center of MassXII. Gravity (Noncontact Force)XIII. WeightXIV. Contact ForcesXV. Ground Reaction Force (GRF)XVI. Center of Pressure (COP)XVII. Linear Kinetics of LocomotionXVIII. Joint Reaction Force (JRF)XIX. Inertial ForceXX. Muscle ForceXXI. Elastic ForceXXII. QuizCurrent LectureI. Outlinea. Forcei. External, internal, inertiab. Newton’s laws of motionc. Momentumd. Center of Masse. Gravityf. Weightg. Types of contract forces in human movementi. Ground/joint reaction force, inertial force, muscle force, elastic force, frictionII. Kinematics vs. Kineticsa. Kinematicsi. Examines spatial (space) and temporal (time) characteristics of motion1. Position (displacement), velocity, and accelerationii. The forces causing the motion are not consideredb. Kineticsi. Deals with the cause of motion – forceii. The concept of force is the basis for understanding linear kineticsiii. Linear kinetics – deals with the causes of translator motionIII. Sources of Forces Affecting Human Movementa. External (environmental)i. Gravityii. Impacts, collisionsiii. Ground/object contact reactions (normal, shear)iv. Fluid (air, water, etc.), Pressure, Viscosityb. Internal (Biological)i. Muscle contractionii. Biomaterial properties (strength, elasticity, inertia)iii. Fluid (air) pressurec. Inertiai. The resistance of any physical object to any change in its state of motion, including changes to its speed and directionIV. Forcea. Forces alter the motion and/or change the shape of an objectb. Forces have both magnitude and directioni. Vectorc. Forces have points of application and lines of actiond. Force has units of Newtons (N), which is kg x m/s2V. Composition and Resolution of Forcesa.VI. Newton’s Laws of Motiona. Published 1687b. Basis for most analyses in biomechanicsc. Laws demonstrate how and when a force creates motionVII. Newton’s 1st Law: Law of Inertiaa. A body tends to stay at rest or in uniform motion unless acted upon by an unbalanced external force!b. Overcoming inertia requires a net external force greater than the objects inertiac. To initiate movement the external force must positively accelerate the objectd. To stop movement external force must negatively accelerate the objecte. Greater mass = greater inertia, requiring larger external forcesVIII. Newton’s 2nd Law: Law of Accelerationa. The change of motion of a body is proportional to the force impressed and is made in the direction of the straight line in which that force is impressedb. Force = mass x accelerationIX. Newton’s 3rd Law: Law of Action-Reactiona. For every action, there is an equal and opposite reaction (on different objects)i. The mutual actions of two bodies upon each other are always equal and directed to contrary partsX. Momentuma. Inertia in motion – or – mass in motionb. Carries the notion of both mass (inertia) and velocity (motion)i. “tendency” of an object to remain in motionii. An object with momentum is going to be hard to stopiii. To stop an object with momentum, it is necessary to apply a force against its motion for a given period of time  impulsec. Momentum = mass x velocityi. Momentum is in the same direction as the velocity ii. Momentum is a vector!iii. Momentum is the quality of motion of an objectiv. Symbolized as pv. Units = kgm/s or Nsvi. Therefore, (with constant mass) to change momentum an external force must be appliedd. Conservation of Momentumi. In a system of bodies that exert forces on each other, the total momentum in any direction remains constant unless some external force acts on the system in that directionXI. Center of Massa. The center of mass is the mean location of all the mass in a systemb. The ground reaction force vector acts through the center of mass of the bodyXII. Gravity (Noncontact Force)a. The force of gravity is inversely proportional to the square of the distance between attracting objects and proportional to the product of their massesi. Two small objects: gravitational attraction extremely small – neglectii. However, the Earth’s mass is considerableiii. The force of gravity causes an object to accelerate towards earth at 9.81 m/s2XIII. Weighta. Weight is the force produced by the acceleration of gravity on an objectb. Weight DOES NOT equal massc. Weight is a vector quantityi. Line of action (straight down) and point of application (CoM)XIV. Contact Forcesa. Contact forces result from the interaction of two objects b. Contact forces:i. Ground reaction force (GRF)ii. Joint reaction forceiii. Inertial forceiv. Muscle forcev. Elastic forcevi. Frictionvii. Fluid Resistance1. Viscosity and densityXV. Ground Reaction Force (GRF)a. If you push against the ground, the ground pushes back with a force equal in magnitude but opposite direction (Newton’s 3rd Law)b. GRF is commonly measured using a force platformXVI. Center of Pressure (COP)a. In biomechanics, COP is the term given to the point of application of the GRF vectorXVII. Linear Kinetics of Locomotiona. Initial peak: rises above BW as weight bearing takes placeb. 2nd peak: active push against ground to move into the next stepc.XVIII. Joint Reaction Force (JRF)a. The force experienced at a jointb. A common biomechanical analysis is a link segment analysisi. Each segment is considered separatelyc. The net force acting across the joint can be determined from the kinematic and kinetic analysesXIX. Inertial Forcea. Force opposite in direction to an accelerating force acting on a bodyb. In many instances in human movement, one segment can exert a force on another segmentc. Movement not