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Unformatted text preview: Lecture 23 pls-23.1 Harmonic Oscillations Media: 1. Wooden block (and several weights) on spring / string 2. Equipment to measure oscillating block 3. Fendt circular motion demo 1. Ideal Spring The ideal-spring force is expressed as ( ) eq x sp x x k F = , where k is known as the spring constant of the spring. x + x sp F , eq x equilibrium position of the end of the spring. x sp F , x sp F , eq x x eq x x eq x x Lecture 23 pls-23.2 Note: (i) Larger k stronger spring. (ii) Minus sign is because x sp F , is in direction opposite to eq x x . (iii) eq x x can be either + or (and x sp F , has opposite sign). 2. Harmonic Motion Demo: measure motion of oscillating block Motion looks harmonic (sine or cosine). Clicker questions 1 . Demo with different amplitude Clicker questions 2 . Demo with different mass If we start the oscillations with an initial displacement A and no initial velocity, then its displacement vs time can be written as ( ) ( ) t A x t x eq...
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