KIN 3309 1st Edition Lecture 23 Outline of Last Lecture I Electromyography EMG II Accelerometers IMU Outline of Current Lecture I Kinematics vs Kinetics II Vectors and Scalars III Linear vs Angular Motion IV Position and Displacement V Important Parameters VI What is a Projectile VII Two Dimensions VIII Types of Angles IX Angular and Linear Position X Angular and Linear Velocity XI Centripetal Radial Acceleration XII Sources of Forces Affecting Human Movement XIII Force XIV Center of Mass XV Weight XVI Types of Forces XVII Torque XVIII Newton s Laws of Motion XIX Free Body Diagrams XX Momentum XXI Moment of Inertia XXII Radius of Gyration XXIII Conservation of Momentum XXIV Linear Impulse XXV Angular Impulse XXVI Linear Work XXVII Angular Work XXVIII Linear Power XXIX Angular Power XXX Linear Energy These 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 XXXI XXXII XXXIII Angular Energy Work Energy Theorem Conservation of Energy Current Lecture I Kinematics vs Kinetics a Kinematics i Examines spatial space and temporal time characteristics of motion 1 Position displacement velocity and acceleration ii The forces causing the motion are not considered b Kinetics i Deals with the cause of motion force ii The concept of force is the basis for understanding linear kinetics iii Linear kinetics deals with the causes of translator motion II Vectors and Scalars a Scalars i Can be described by magnitude ii E g mass distance speed volume b Vectors i Have both magnitude and direction ii E g velocity force acceleration iii Vectors are represented by arrows III Linear vs Angular Motion a Linear Motion i AKA translation or translational motion ii Movement on straight or curved pathway iii All points on a body move same distance same time b Angular Motion i Motion around some point ii Different regions of the same body segment do not move through the same distance IV Position and Displacement a Position i Defines an object s location in space relative to some reference ii A scalar not to be confused with displacement b Distance i A scalar ii Change in position without direction c Displacement i Defines the change in position ii Displacement is a straight line between start and finish iii Displacement is a vector V Important Parameters a Position WHERE i Location in space relative to some reference point ii Linear and angular position b Displacement Distance HOW FAR i Displacement 1 Final change in position 2 Vector quantity ii Distance 1 Sum of all changes in position 2 Scalar quantity c Velocity and Acceleration i Velocity HOW FAST 1 Vector quantity 2 Change in position time ii Acceleration HOW QUICKLY IS VELOCITY CHANGING 1 Vector quantity 2 Change in velocity time VI What is a Projectile a An object that is only acted on by i Gravity ii Air resistance b We have no control over the object once we lose contact with it c Thrown implements ball discus shot and airborne humans long jump high jump can be projectiles VII Two Dimensions a The parabolic trajectory of projectiles i Vertical velocity is zero at peak height ii Horizontal velocity is unchanged iii Peak height occurs at total horizontal distance and at total time when starting and ending at the same height VIII Types of Angles a Absolute Angle i An absolute angle is measured from an external frame of reference b Relative Angle i A relative angle is the angle formed between two limb segments IX Angular and Linear Position a The linear displacement can be determined when the length of the segment radius and the angular displacement are known X Angular and Linear Velocity a The linear velocity can be determined when the length of the segment Radius and the angular velocity are known XI Centripetal Radial Acceleration a Even at constant angular velocities the direction of the linear velocity changes when going around a curve b Since velocity is changing there must be acceleration c This acceleration is towards the center of rotation i Called centripetal acceleration XII Sources of Forces Affecting Human Movement a External environmental i Gravity ii Impacts collisions iii Ground object contact reactions normal shear iv Fluid air water etc pressure viscosity b Internal biological i Muscle contraction ii Biomaterial properties strength elasticity inertia iii Fluid air pressure c Inertia i The resistance of any physical object to any change in its state of motion including changes to its speed and direction XIII Force a Forces alter the motion and or change the shape of an object b Forces have both magnitude and direction i Vector c Forces have points of application and lines of action d Force has units of Newtons XIV Center of Mass a The center of mass is the mean location of all the mass in a system XV Weight a Weight is the force produced by the acceleration of gravity on an object XVI b Weight does not equal mass c Weight is a vector quantity Types of Forces a Ground Reaction Force GRF i Force exerted by the ground on a body in contact with it b Joint Reaction Force i Force experienced at a joint c Inertial Force i Force opposite in direction to an accelerating force acting on a body d Muscle Force i Force when muscle fibers generate tension e Elastic Force i The tendency of solid materials to return to their original shape after being deformed f Friction Force i The force acting parallel to the interface of two contacting surfaces during motion or impending motion XVII Torque a Torque is often referred to as rotary force and is the angular equivalent of linear force b Torque is the product of force F and the perpendicular distance d from the force s line of action to the axis of rotation i Vector c The units of torque are newton meters XVIII Newton s Laws of Motion a 1st Law Law of Inertia i A body tends to stay at rest or in uniform motion unless acted upon by an unbalanced external force nd b 2 Law Law of Acceleration i Force mass x acceleration ii Torque moment of inertia x acceleration c 3rd Law Law of Action Reaction i For every action there is an equal and opposite reaction on different objects XIX Free Body Diagrams a Called a force diagram i To analyze the forces and moments acting on a body XX Momentum a Inertia in motion or mass in motion b Carries the notion of both mass inertia and velocity motion i Tendency of an object to remain in motion c Momentum mass x velocity i Momentum is in the same direction as the velocity ii Momentum is