1. Back & forth & back & forth Are you getting sleepy?

2.  X = displacement – distance pulled/stretched from equilibrium  When released – spring exerts a force on the mass towards equilibrium  V max @ equilibrium  p causes it to overshoot  @ max stretch/compression –  V = 0, acceleration & force @ max

3.  F elastic = -kx Pendulums

4.  Disregard mass of string, air resistance, friction  If restoring F proportional to displacement = harmonic motion  Small angles of displacement equal simple harmonic motion  Free body diagrams (miss them?!) to Resolve into x & y components