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Linear Kinetics

Law 1 of Inertia: object at rest and no external forces acting on it remains at rest, object in motion stays in motion, object at rest stays at rest, Law 2 of Acceleration: Change in motion is proportional to the force impressed and is made in direction of straight line. Force causes acceleration Law of Reaction: forces never act in isolation, but in pairs, forces equal to magnitude, in opposite direction. Conservation of Momentum: momentum before impact equals momentum after impact Impulse-momemtum: Ft=m(VF-VI) M=mv I=Ft

Torques & Moments

Torque: turnin effect produced by force aka moment, angular or rotary force, directly proportional to magnitude of force. Motion of a restrained system, force applied away from axis. Moment arm: shortest distance betwen axis of rotaiton and line of action or force Lever: distance btwn pt of force app and axis of rot. Torque in humans: muscle Rotary component: perpen to bone segment, creates internal momemnt cause motion Nno rotary: perpen to rotary comp paralle to bone, does not contribute to internal moment compression, causes joint compression Moment/torque depedent on: muscle force, lever arm, angle of pull Equilibrium: state characterized by balanced forces and torques Stability: statically maintained as long as the vertical porgjection of COG remains within base of support 1st class lever: axis btwn motive force and resistive(MAR) ex: elbow extension, plantar flexion 2nd class: resistance in middle(ARM) ex push up 3rd: motive force in middle(AMR) mechanical advantage: Force of muscle must be greater than resistance force

Angular Kinematics

3 units: Degrees, revolutions or rotations, 1 rad=57.3 deg. Radian: ratio of arc length of a circle to radius length. Radians is a dimensionless measure. 3 pieces linear-angular motion: axis of rotation, radius of rotation, kinematics in radians Increase radius of rotation= Increase linear displace