Cdu Thay A^^ = |amgs = ^ m g ( A - x ) ; k = co^m, t a difdc: — mco^A^ = L i m g ( A - x ) + — m v ^ + —mco^x^ o - c o ^ A ^ = u g ( A - x ) + - v ^ +-co^x^ « v _ ^ 7o)W-2^g(A-x)-co^x^ Thay so vdri co = J — = , 1—^ = V S O ta c6: v,^^ = , - , , - ^ = 0,4V2m/s = 40V2cm/s Vay c/ipn dap an D 34: Dao dong tong hcfp cua h a i dao dong dieu hoa cung phtfcfng, ' 571^ (cm) d o n g thuf n h a t c6 phiTofng t r i n h l i d o x, = c o s (cm) cung t a n so c6 phifcfng t r i n h l i x = 3cos ut Biet dao Dao dong thuf h a i CO phi/cfng t r i n h l i l a : A x , = c o s C X2 =2 cos 7rt + — 5n Trt (cm) J (cm) B X , =2cos D X2 = cos 6, ^ Trt V (cm) 571 (cm) Giai TCr g i a n vectcf, bieu d i e n cac dao dong bSng cac vector A , , A , v a A T a t h a y dao d o n g t o n g h o p A ngiroc p h a v d i dao d o n g A, V i v a y dao d o n g A j p h a i ngifgrc p h a vdi A, va cung p h a vdi A Tir d6 t a c6: A2 = A i + A = c m 72 Giai Chi ti^t 06 thi T S DH, CD M6n V$t II