cua He I a n lifOt l a 0,4 s va cm Chon true x'x t h i n g duTng chieu ducrng hifdng xuong, goc t o a t a i v i t r i can b k n g , goc t h i gian t = k h i v a t qua v i t r i c a n b ^ n g theo c h i e u difdng L a y g i a to'c r o i tii g = 10 m/s^ v ^ 7t^ = 10 Thori gian ng^n n h a t ke tijf k h i t = den k h i ILTC d a n h o i cua 16 xo c6 I6n ale t i e u l a : A ^ s 30 B ±s 15 C Is D 10 -s 30 GiSi Chu k i : T = 2% CO = STC CO K h i treo v a t vko, 16 xo g i a n m o t doan: A / = — g = = 0,04m < A = 0,08m k CO LLTC d^n h o i cua 16 xo c6 l t a c6 phuomg t r i n h dao dong: X = sin 57rt => sin 57rt = - sin 57rt =-0,5 57rt = - — + k t Vdy chon dap an A Cdu 30: D a t vao h a i dau doan mach dien R L C k h o n g p h a n n h a n h m o t hieu d i e n t h e u = 220V2cos c o t - i ^ ( V ) t h i C L r n g d6ng dien qua doan mach c6 bieu thiJc l a i = l-Jlcos ( A ) Cong sua't tieu t h u cua doan mach n a y l a : A 2 V W B 440W C 4 V W D 220 W G\k\ Dp lech pha giuTa ciTdng dong di^rt v a h i e u dien t h e : V2 ^2 n ^ 14 Giai chi.tigf 66 thi TS DH, CD M6n VHt II