... 43(cm/s) 2. 2 (d1 + d2 ) vA vB = 320 cos ( ) sin (40t ) 6 { Cõu 49 ỏp ỏn D t t = v v = v 0,866c c2 c { t = t Cõu 50 ỏp ỏn B vmax A= = 22 A2 = A2 + A2 + 2A1 A2 cos (2 ) = 22 + 22 + 2. 2 .2 cos ... 9H2 4H1 = H2 = 0,96 Cõu 16 ỏp ỏn C 0 ,21 0,15 2m1 + 2m + = 5(2n + 1) (mm) x = (2m1 + 1) = (2m2 + 1) = { 2m2 + = 7(2n + 1) 2 2m2 + 0 ,21 x = 5(2n + 1) = 1,05n + 0, 525 (mm) Cõu 17 ỏp ỏn D 1000 .2 ... 14. . .27 2 s 15. . .28 1 s 16. . .28 7 s 17. .. 29 0 s 18. . .29 8 s 19. ..306 s 20 . ..310 s 21 . ..318 s 22 . .. 322 s 23 . .. 328 s 24 . ..334 s 25 . ...