dp dien triTcfng c6 dp Idfn E = lO^V/m va hi/dng t h a n g dufng xuong dudti Lay g = 10 m/s^, n = 3,14 Chu k i dao dpng dieu hoa cua lac l a : A 0,58 s B 1,99 s ' C 1,40 s D 1,15 s Giai Con lac ngoai chiu tac dung cua t r p n g lyc P = m g chiu tac dung cua life dien F = qE , mg + qE qE ,^ S I O ' I O ' , ^ K h i g = — ^ — — = g + — = 10 + — — = 15(m/s-j IQm m Chu k i T = Vdy chgn dap an D Cdu 50: Trong t h o n g t i n l i e n lac bang song v6 t u y e n , ngifdi t a sijf dung each bien dieu bien dp, tufc la l a m cho bien dp cua song dien tii cao t a n (gpi la song mang) b i e n t h i e n theo thori gian vdfi t a n so b k n g t a n so cua dao dpng a m t a n Cho t a n so song mang la 800 k H z K h i dao dpng am t a n c6 t a n so 1000 Hz thifc h i e n m o t dao dpng toan p h a n t h i dao dpng cao t a n thiic h i e n difpc so' dao dpng toan p h a n l a : A 800 B 1000 C 625 D 1600 Giai So dao dong cao t a n thiTc h i e n : N = • • = goO 1000 Vdy chgn dap an A Cdu 51: M o t b a n h da c6 momen quan t i n h doi vdfi true quay co d i n h cua no la 0,4 kg.m^ De b a n h da t a n g toe tii t r a n g t h a i dufng y e n den toe dp goc (0 p h a i t o n cong 2000 J Bo qua ma sat Gia t f i cua co l a : A 10 rad/s B 200 rad/s C 100 rad/s D 50 rad/s Giai Dpng n a n g cua b a n h da: Wd = ^/co^ Dpng n a n g cua b a n h da bang c h i n h cong da cung cap: Wd = A Suy r a M = , 2A 2.2000 = 100 rad/s Vdy chgn dap an C Giai chl tiet de thi TS BH, CD Mon Vat li 79