Spring: deformation x; km氵y氵 Body displacement x; 平衡位置 force: F=-kx(frictionless); Fig.15-1 acceleration F 2 =-=-0x→ =-0x =k dt 2 which solution is x=:A cos(at or: x =: Asin(at+ 9=9 2 This equation is called the harmonic equation.Spring: deformation x; Body: displacement x; force: (frictionless); acceleration: F = −kxx m F a  = = − which solution is   = + = + = +     x Acos(t  ) or x Asin(t  ) This equation is called the harmonic equation. k m x Fig.15 −1 x dt d x a     = = − m k  =