Cdu 24: T a i t h i d i e m t , d i e n a p u = 200^2 cos ( t r o n g u t i n h b a n g V , t t i n h b a n g s) c6 g i a t r i 100>/2 V v a d a n g g i a m Sau thofi d i e m 300 s, d i e n a p n a y c6 g i a t r i l a : A -IOOV2 V B -lOOV c looVs V D 200V Giai K h i t = t i t a c : u = 200^2 cos l O O T r t - = 100V2 cos] 0 ; r t - ^ = i « 0 r t - ^ = ^ 2 T a c6: T = 271 CO 2TI IOOTT \ 50 K h i At = ^ { s ) = - ( s ) 300^ ' 6^ ^ K h i t2 = t i + A t t h i : 71 271 T u , = 0 ^ cos — + — — T Vdy chon = 2OOV2 C O S y = -IOOV2 ( V ) dap an A Cdu 25: X e t h a i m a c n d a o d o n g d i e n tCr H tiTotng C h u k i dao d o n g r i e n g cua m a c h thuf n h a t l a T j , c u a m a c h thijf h a i l a T2 = T i B a n d a u d i e n t i c h t r e n m o i b a n t u d i e n c6 d o 16n cifc d a i QQ S a u m i t u d i e n p h o n g d i e n q u a c u o n c a m c u a m a c h K h i d i e n t i c h t r e n m o i b a n t u cua h a i m a c h d e u c6 d o Idfn b k n g q (0 < q < Qo) t h i t i so lorn ciicfng d o n g d i e n t r o n g m a c h thuf n h a t v a I6n c i r d n g d o n g d i e n t r o n g m a c h thuf h a i l a : A c.i B D Giai G i a suf d i e n t i c h t r e n cac t u b i e n t h i e n t h e o q u y l u a t „ _ 271 dq 271 ^ 271 q = Qo coscot = Qo c o s — t ^ = - - = - — Q ^ sm — t 1 at r Do'i v d i m a c h thuf n h a t k h i t i d i e n t i c h c6 I6n l a q t a c : 66 Giai Chi tiS'tde thi TS OH, CD Mon Vatii