Vay chon dap an B.. Vdy chgn dap an D.. Vdy chon dap an C.
Trang 1Giai
Do boi giac cua k i n h l a : G = ^ = — = 20
• 0,06 Goc t r o n g t h i e n the k h i khong dung k i n h l a : = ^ = = 0,25'
Vay chon dap an B
Cdu 51: M o t v a t r a n quay quanh mo t true co d i n h d i qua v a t co phtfcfng
t n n h chuyen dong (p = 10 + t^ (cp t i n h bang rad, t t i n h b k n g giay) Toe
do goc va goc ma v a t quay ducfc sau t h d i gian 5 s ke tCf thcfi diem t = 0 Ian lirgft la:
A 5 rad/s va 25 rad B 5 rad/s va 35 r a d
C 10 rad/s va 35 rad D 10 rad/s va 25 r a d
Giai
So sanh phifdng t r i n h cp = 10 + ( c p t i n h b k n g rad, t t i n h bkng giay)
vdi phifotng t r i n h t o n g quat (p = % + (ii^t + ^yt^ t a difdc cac gia t r i :
(Po = lOrad/s; © 0 = 0; = 1 =:> Y = 2rad/s\
M a t khac, phicfng t r i n h toe do goc: co = yt •
Sau 5s, t a co: co = 2.5 = 10 rad/s
A(p = (p-cpo =10 + t ^ - 1 0 = 25rad
Vdy chgn dap an D
Cdu 52: M o t dia p h i n g dang quay quanh true eo d i n h d i qua t a m v^
vuong goc vcri m a t phang dia v d i toe do goe k h o n g ddi M o t diem b a t
ky n k m d mep dia
A khong CO ca gia toe hudtng t a m va gia toe tiep tuyen
B CO ca gia tdc hudfng t a m va gia toe tiep tuyen
C chi c6 gia toe hifdng t a m m a k h o n g co gia tdc tiep tuyen
D chi CO gia tdc tiep tuyen m a khong co gia tdc hirdrng t a m
GiSi
M o t diem ba't k y n k m d m6p dia chi co gia tdc hifdng t a m m ^
khong CO gia tdc tiep tuyen
Vdy chon dap an C