5.一弹簧振子作简谐振动,其振动方程为 =Acos (omega t+dfrac (1)(2)pi ). 则该物体在 t=0 时刻的动-|||-能与 =dfrac (T)(8)(T 为周期)时刻的动能之比为 ()-|||-(A)1:1 (B)3:1 (C)2:1 (D)1:2