bài tập điểm 9-10 chương dao động cơ hoc vật lý 12 (buổi hoc số 3)

GV: NGUYEN DUC ANH - 0972 113 246   ng Nai) Facebook: Vat LY Luyen Thi m 9  u hc ( bui hc s 1 ) 1 Mt vt nh ng M = 0,9 (kg), g th cng i c nh. Mt vt nh ng m=0,1 (kg) chuyng theo ng vi t 0,2 2 n va chm mm vi M. Sau va chm hai v i trc cy gia tc trng g=10m/s 2   A 4,5 cm B 4 cm C 4 2 cm D 4 3 cm Gii: Vn tc ca hai vt sau va chm: (M + m)V = mv > V = 0,02 2 (m/s) Sau va chm: x 0 = mg k = k mg = 0,04m = 4cm A 2 = x 0 2 + 2 2  V = x 0 2 + k mMV )( 2  = 0,0016 > A = 0,04m = 4cm  2 : Con lm vt n cng k = 200N/m, lt trc th v bt m = 200g t  cao h = 3,75cm so v do, va chm mm v, ly g = 10m/s 2 Sau va chm hai vn gc t ti v ng ca h, chi vi gian t = ng ca h hai v A. x = 1,08cos(20t + 0,387)cm. B. x = 2cos(20t + 4  )cm. C. x = 1,57cos(20t + 0,155)cm. D. x = 2cos(20t + 3  )cm Gii: Vn tc ca vt m khi va ch v = gh2 Vn tc v 0 ca h hai vt sau va chm: (M+m)v 0 = mv > v 0 = mM ghm  2  a h hai v ng ca h x 0 -  0 = m g k = 0,01m = 1cm  ng ca h: A 2 = x 0 2 + 2 2 0  v Vi  = mM k  = 5,0 200 = 20 (rad/s) A = 2 2 0 2 0 x  v  = 2 2 20 12,0 0,01  = 0,02 m = 2cm m M  O m h M + GV: NGUYEN DUC ANH - 0972 113 246   ng Nai) Facebook: Vat LY Luyen Thi ng ca h hai vt x = Acos(20t +) khi t = 0 x = x 0 = A/2 > cos = 0,5 >  = 3  > x = 2cos(20t + 3   3: Con li vt n .Mt vt nh khn va ch vt M sau va chm 2 v a h  A.Wo/5 B.Wo C.4Wo/5 D.W0/4 Gii: Vn tc v 0 ca vc khi va ch W 0 = 2 2 0 mv > 0 v = m W 0 2 = 2 M W 0 2 Vn tc v ca h hai vt sau va chm: (M + m) v = mv 0 > 4 5 Mv = 4 1 Mv 0 > v = 5 0 v = 0,4 M W 0 2 ng ca h  W = 2 )( 2 vmM  = 4 5 2 M v 2 = 4 5 2 M .0,16. M W 0 2 = 0,2W 0 = W 0  4.    2   A. 15 cm B. 20 cm C. 10 cm D. 12 cm Gii: G O M x m O h GV: NGUYEN DUC ANH - 0972 113 246   ng Nai) Facebook: Vat LY Luyen Thi Vn tc cc khi chm M: v 0 = gh2 = 18 = 3 2 m/s Gn tc cm MV + mv = mv 0 (1) vi v 0 = - 3 2 m/s 2 2 MV + 2 2 mv = 2 2 0 mv (2) T  3 2 v 0 = - 2 2 m/s > V max = 2 2 m/s Tn s ng :  = M k = 2,0 20 = 10 2 rad/s  ng : A =  max V = 210 22  5.  2   m   A. 2,5 cm B. 2 cm C. 5,5 cm D. 7 cm Gii:G ng  t  VTCB  k mg  k gmm )(  -  k gmm )(  - k mg = k mg = 100 10.15,0 0,015m = 1,5cm   6 : Mt con lt nm ngang gm v s c ng v 5cm. Khi M qua v i ta th nh v  ng v A. 25cm B. 4,25cm C. 32cm D. 22cm Gii: Tn s a con lc:  = M k = 4,0 40 = 10 rad/s. T ca M khi qua VTCB v = A = 50 cm/s  M  O   m GV: NGUYEN DUC ANH - 0972 113 246   ng Nai) Facebook: Vat LY Luyen Thi T c mM Mv  = 40 cm/s Tn s a h con lc:  mM k  = 5,0 40 = 5 20 rad/s.  ng ca h ' '  v = 2 5  .    2   A. 15 cm B. 20 cm C. 10 cm D. 12 cm Gii: G O M x m O h GV: NGUYEN DUC ANH - 0972 11 3 246  .  k gmm )(  -  k gmm )(  - k mg = k mg = 10 0 10 .15 ,0 0, 015 m = 1, 5cm   6. GV: NGUYEN DUC ANH - 0972 11 3 246   ng Nai) Facebook: Vat LY Luyen Thi m 9  u hc ( bui hc s 1 )  1 Mt vt nh ng