The acceleration of the particle executing S.H.M. at any instant, is defined as the rate of change of its velocity at that instant. So acceleration

Important Points

 (i) In S.H.M. as

is not constant. So equations of translatory motion can not be applied.

(ii) In S.H.M. acceleration is maximum at extreme position.

From equation (i) 

(iii) In S.H.M. acceleration is minimum at mean position

From equation (i)