The Simple Pendulum. Recall that the torque due to gravity about the rotation(z) axis Isτ=la=-mgd d=Lsin0≈ Le for smal|0 soτ=-mgL0 melo= mLa Butτ=lo,/=mL2 a=-00 where VL m Same equation as for simple harmonic motion d 0=0ocos(ot+φ) mg Physics 121: Lecture 22, Pg 4Physics 121: Lecture 22, Pg 4 The Simple Pendulum... Recall that the torque due to gravity about the rotation (z) axis is  = Ia = -mgd. d = Lsin   L for small  so  = -mg L But  = Ia  I = mL2  L d m mg z  a 2 − mgL = mL a   2 = −  = g L where Same equation as for simple harmonic motion !  = 0 cos(t + )