Motion in 1-Dimension ? Dynamics: study of motion and of physical concepts such as force and mass ? Kinematics: part of dynamics that describes motion ? 1-D motion: motion along a straight line. Described in a frame of reference ? Basic quantities to describe the motion: ? position [m] ? velocity [m/s] ? acceleration [m/s2] ? velocity and acceleration can be instantaneous or averaged over a certain amount of time ? distance does not equal displacement ? speed does not equal velocity ? Scalar: has a mafnitude but no direction (ex. distance, speed...) ? Vector: has a magnitude and a direction (ex. velocity) ? Displacement is the change in position ? Î?x = x(final) - x(initial) ? SI unit (m) ? displacement is the change in position between 2 instants, regardless of what happened in the middle ? Distance does not equal displacement ? distance is the accumulated travel over a certain time interval SI unit (m) ? Average speed (scalar) ? distance traveled divided by time interval ? average speed = distance/Î?t ? Average Velocity (vector) ? displacement divided by time interval ? v= Î?x/Î?t ? Average acceleration (vector) ? change in velocity during Î?t SI unit m/s2 ? a = Î?v/Î?t ? Equations at Constant Acceleration ? a(final) = a (inital) SI unit m/s2 ? v (final) = v(inital) + a(inital)*Î?t SI unit m/s ? x(final) = x(inital) + v(inital)*Î?t + 0.5*a(inital)Î?t2 SI unit m ? Other useful equations ? x(final) = x(inital) + 0.5(v(final)+v(inital))*Î?t SI unit m ? v(final)2= v(initial)2 + 2a(inital)Î?x SI unit m2/s2 ? Freely Falling Objects ? Objects moving freely under influence of gravity alone (no air resistance) ? acceleration is constant and equal for all objects ? at earth surface free fall acceleration is g=9.80 m/s2 ? still called free fall when object is thrown upward initially ? free fall is a particular case of constant acceleration with a=-g nothing more
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