1Linear KineticsCHAPTER 3Basic Dimensions Need common units of measure for quantitative analysis Qualitative variables have quantitative counterparts LENGTH TIME SPACE OTHERSLENGTH Describes position in space Critical component of sport1) Anthropometrics2) Equipment3) Dimension of sport4) International system used5) METER (m)TIME Important dimension in sport Performance measure Initial or start time Final or end time SECONDS (s)Other Descriptors Mass Inertia Weight Force Length, Time, & Mass are the BASIC dimensions used in mechanics Everything else is derived from these 3 MASS (m)- quantity of matter composing a body WEIGHT (N or lb)- gravitational forceacting on a body; proportional to m …wt = mag INERTIA - resistance to action, change, to move; directly proportional to mass FORCE - push or pull acting on a body; magnitude direction & point of application2FORCE any interaction (push or pull) between two objects that can cause an object to accelerate either + or - magnitude (vector) direction (angle) pt. of application line of actionNEWTON’S LAWS Sir Isaac Newton Born the year Galileo died Cambridge educated The Black Plague 1686 ~ PrincipiaLaw of Inertia A body will maintain a state of rest or constant velocity unless acted on by an external force that changes the state Principle of Conservation of MomentumMechanical Behavior of Bodies in Contact Linear Momentum: Quantity of Motion M = mv Units - kg • m/sPrinciple of conservation of momentum:In the absence of external forces, the total momentum of a given system remains constantMechanical Behavior of Bodies in Contact Newton:When two bodies undergo a direct collision, the difference in their velocities immediately after impact is proportional to the difference in their velocities immediately before impact-e = relative velocity after impact = v1-v2relative velocity before impact u1-u2Mechanical Behavior of Bodies in Contact Impact:Perfectly elastic impact: -e ≈ 1Perfectly plastic impact: -e ≈ 0Coefficient of restitution:Absolute value of the ratio of the v of separation to the v of approach3Law of Acceleration A force applied to a body causes an acceleration of that body of a magnitude proportional to the force, in the direction of the force, and inversely proportional to the body’s mass F = ma ~or~ a = F / mMechanical Behavior of Bodies in Contact Impulse: Impulse = FtDerived from Newton’s Second law: F = ma F = m ([v2-v1] / t) Ft = (mv2) - (mv1) Ft = ∆MLaw of Reaction For every action, there is an equal and opposite reaction When one body exerts a force on a second, the second body exerts a reaction for that is equal in magnitude and opposite in direction of the first bodyLaw of Gravitation All bodies are attracted to one another with a force proportional to the product of the masses and inversely proportional to the square of the distance between them Fg= G(m1m2/
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