... trờn bn dng lỳc y l:A. q = 20.1 0-9 cos(2.105 t -/ 3) (C) B. q = 20.1 0-9 cos(2.105 t +/ 3) (C) C. q = 2.1 0-9 cos(2.105 t +/ 3) (C) D. q = 20.1 0-9 cos(2.105 t -/ 6) (C)Cõu 23: Chn cõu sai.A. ... mụt iờm bng 1,8W/m-2. Hoi mụt song õm khac co cung tõn sụ , nhng biờn ụ bng 0,36mm thi se co cng ụ õm tai iờm o bng bao nhiờu?A. 0,60W/m-2B. 2,70 W/m-2C. 5,40W/m-2 D. 16,2W/m-2Cõu 20: Khi chiờu ... Ti mt thi im t no ú vt ang i qua v trớ cú li x= -2 3cm theo chiu õm ca trc to . Hóy tỡm li v vn tc ca vt sau ú 0,25s A. x= -3 ,86cm v v = 3,25cm/s B.x= 3,86cm v v = -3 ,25cm/s C. x= -3 ,86cm...