A.振幅减小,周期减小,机械能减少 B.振幅减小,周期不变,机械能减少 C.振幅不变,周期减小,机械能减少 D.振幅不变,周期不变,机械能减少
A.35.3° B.40.9° C.45° D.54.7°
A.mf′ B.f′/m C.(1+1/m)f′ D.(1-1/m)f′
A.1.732 B.1.50 C.1.414 D.1.33