Cau 8: Mot chat diSm dao dong dieu hoa tren true Ox theo phuong trinh x = 4eos47rt x tinh bing cm, t tinh bang s.. Dao dong tong hop cua vat la mot dao dong dieu hoa cung tan so, c6 bien
Trang 2NHA XUXT BAN DAI HpC SIT PHAM TP Hb CHf MINH
280 An Di/ang Vi/ang, Phw&ng 4, Qugn 5, TP Ho Chi Minh
Di?n thogi: (08) 38 301 303 - Fax: (08) 39 381 382
Email: nxb&hcmuo.edu.vn Website: httD://nxb.hcmuD.edu.vn/
Vft ly 12
T6m tit ly thuyet B^i tgp trie nghifm
(Tgpl) Tac gia: ThS Vd Mgnh Hung
Chju trach nhi$m xuat ban:
Glim doc-T6ng blen tip PGS TS NGUYIN KIM HSNG
Bien tgp ngi dung:
In 1000 cuon kho 16 x 24 cm tgi Cong ty TNHH MTV In an Mai Thjnh Ou-c
Dang ky ke hogch xuat b^n so 845-2012/CXB/02-168/DHSPTPHCM. Quyt
djnh xuat ban so 500/QD-NXBDHSP ky ng&y 06 thing 09 n3m 2012 In xon
va nop lu'u chieu thing 12 nSm 2012
L O f l N O I D A U
Than chao quy thay c6, cac bac phu huynh va cac em hoc sinh lop 12! Nh3m givip cac em hpc sinh c6 them tai lieu ciing c6 kien thuc va ren luyen ky nang giai cac bai tap Vat l y dS chuan bi cho cac ky thi t6t nghiep
Trung hoc Ph6 thong, tuyen sinh Dai hpc va Cao dSng, chiing toi da smi tam va
bien soan bo sach Tom tat ly thuyet va b^i tap trSc nghif m V a t ly 12
Bo sach gom hai tap:
T a p 1: Dao dong ca Song ca va Dong di?n xoay chieu
T a p 2: Dao dgng di?n tir Song anh sang, Lugmg t u anh sang va
Hat nhan nguyen t u
M o i tap sach dugc chia lam nhi§u chirong M o i chuong dago phan
loai theo timg van de trpng tam ma hoc sinh can n i m vGng Trong timg \kn
&k, n o i dung l y thuyet dugc tom tat mpt each ngSn ggn nhSt, sau do la bai
tap mau c6 giai c h i tiat va mgt s6 cau trac n g h i f m lien quan Sau m o i
chuong, CO khoang 100 cau trdc nghi?m de hpc sinh o n tap tung vSn de
dugc neu ra
Trong bg sach T o m t § t ly thuyet v a bai tap trSc nghifm V a t ly 12
CO suu tam mot so cau t r i e nghiem t u cac da thi tot nghiep Trung hoc Pho
thong, tuyan sinh Dai hgc va Cao d i n g cua Bg Giao dye va Dao t^o de cac
em hgc sinh t h u sue
Mac du da c6 gang bian soan k y , nhung chdc chan se khong tranh kh6i nhung sai sot M o n g quy dgc gia thong cam va gop y da i k tai ban dugc
hoan thien hem
Chung t o i hy vgng bg sach nay se dong gop mgt phdn quan trong
3ng qua trinh hgc t§p cua cac em hgc sinh Chuc cac em hgc t|ip tot!
' Tac gia:
T h S V 6 M a n h Hung
Trang 3MVC LUC
L 6 I N 6 I D A U
CHUONG 1: DAO DONG C O HQC
V4n de 1: Dao dpng di^u hda
Vin de 2: Th(n gian, pha ban d^u trong dao d^ng di^u h6a
Vin dk 3: Con iSc 16 xo
DI 4: DOng nSng, thi nang ca nSng
Vdn De 5: Lyre d^n h6i - Lye k€o \h
Van E>k 6: Con I5c don
D^ 7: T6ng hfjfp dao dOng
Vin De 8: Dao dOng tat dlln wk dao dpng cuSng biic
Bhi t§p trac nghif m t6ng hgrp Chuomg 1
Dip in Chuang 1
CHl/ONG 2: S6NG C O
Vdn d^ 1: Djnh nghia s6ng ca
d^ 2: Qud trhih truyen s6ng - DO l?ch pha - Phuong trlnh truy^n s6ng
Vin 6k 3: Giao thoa song vdi 2 ngu6n k^t hijrp cung pha
V4n ih 4: S6ng dung
via dl5:S6ngam
Bhi t§p trac nghi§m t6ng h(jrp Chuong 2
Dip &n Chuong 2
CHL/ONG 3: D6NG Dl^N XOAY CHIEU
Vkn de 1: C&c bilu thurc ca bin
win ik 2: Do?ui m^ch kh6ng phSn nhinh
d^ 3: Cong sudt - Hf s6 c6ng sudt
Vdn dl 4: M?ch cpng hudng
win de 5: CuOn d&y khOng thu^ ckm
Van d^ 6: Bien thien R, L, C
V ^ d^ 7: Phuong phip giin 6h Vecta
Vin dh 8: M&y phdt difn, dOng co difn, m&y biln thi, truyk t&\n nang
Bai t§p trac nghifm tong hgrp Chuong 3
DAO DONG CO HOC
VAN DE 1: DAO DONG DIEU HOA
o A: Bien do dao dpng (L = 2A: chieu dai quy dao)
o CO: Tan so goc (rad/s)
6> = 2nf = 2n
o f: Tan so (Hz) So dao dong tren mot gidy
o T: Chu ki (s) Thai gian thuc hien mgt dao dong
o (p : Pha ban d^u (phu thuoc vao each chon goc thai gian)
o x: Li do, do dai cua vat so vai vi tri can bang
Vsln toe, gia toe:
a Van t6c: v = x' = - Acosin(cot + (p)= Acocos(a)t + 9 + ^)
^ IV Inax = Aco khi X = 0 (tai VTCB)
^ v = 0 khix = ±A (tai vi tri bien)
b Gia t6c: a = v' = x" = co^Acos(a)t + cp + rr) = - co^x
^ a Lax = to^A khi X = ± A (tai vi tri bien)
Trang 4CHKflM61:DAB OflNECdHqC VAT lY 1? - T O M T A T lY THttYgT V A B A I T A P T B A C H E H I E M - T A P 1 VAT LY 12 - T D M T A T L Y THUVfT «A B A I T A P T B A C W E K I E M - T A P 1 CHI/fl«G1: DAB fi^K CtfHpC
Nhan xet:
• Li do X, van tSc v va gia tSc a biin thien dieu hoa ciing chu ki va
tan so
• Van (6c v sam pha hem li do x mot gdc -
• Gia tdc a sam pha han van toe v mot gocj^
• Gia tSc a ngugrc pha vai li dg x
Bai tap mau: Mot vat dao dong di^u hoa voi phuong trinh x = 5cos
Ant + n cm, t tinh bang giay Goc toa do tai vi tri can bSng
a Xac djnh bien do, chiSu dai quy dao, tin so goc, tan s6, chu ki,
pha ban dau
b Tinh li do x tai thai diem t = 0,25 s
c Viet bilu thuc eua van t6c v, gia toe a theo thai gian t
d Xac dinh cae gia tri van toe, gia t6e eua ehdt diim tai thai
dilm t = 0,25s
c Tinh do Ian van t6e eua chSt diem khi qua vi tri can bSng va do
Ian gia t6e ciia chit dilm khi a vi tri bien
f Tinh van toe khi chit diem c6 li do x = 3cm
g Tinh li do khi chat dilm c6 van toe 127r em/s
h Tinh van toe khi chdt dilm c6 gia t6c a = 4871^ cm/sl
Giai: x = 5cos Ant H— 2 em
a -4 = 5cm; L = 2A- 10cm; a> = 4rr rad/s
Cau 1: Chon phat bieu dung noi ve vat dao dong diSu hoa
A Van toe va li do ngugc pha nhau
B Van toe va gia t6c cung pha nhau
C Li do va gia toe vuong pha nha
D Van toe va gia toe vuong pha nhau
Van t6e ciia chat dilm dao dong diSu hoa c6 do Ian cue dai khi
A li do eua chat diem eo do Ian cue dai
B li do eua chat diem bang khong
C gia toe eua chat diem c6 do Ian cue dai
D pha cua dao dpng e\rc dai
Mot vat dao dpng dieu hoa vai phuong trinh x = 6cos(4;:r)em, ehilu dao cua vat la:
A 4cm B 12cm C 4m D 6m
Cau 4: Mot chdt dilm dao dpng dieu hoa vai phuang trinh x - 5cos(4;rt)
cm S6 dao dpng vat th\rc hi?n duprc trong 5 s la:
§ A 10 B.20 C.5 D 100
Cau 5: Mot chat diem dao dpng dieu hoa vai phuang trinh x = 5cos(2;zf)
gm, li dp cua chat dilm tai thai diem t = 1,5 s la:
A 1,5cm B.-5cm C 0cm D.-6cm
Trang 5CHIfttWe 1: BAO D$l»6 Cd HgC VAT lY I Z - T I J M T A T LY THUYfTVA B A I T A P T B A C WSHlgM - T A P 1 VAT LY 1 Z - TdM TAT LY THUYfl VA B A I T A P T R A C UGHIgM - T A P 1 CHifams 1: BAD oOwGCdHqc
Cau 6: V^n toe cua mpt ehat diem dao dong dieu hoa c6 bieu thuc
V = 50sin(l0t) cm/s, bien dp dao dpng eua chat dilm la
A 2,5 em B 5cm C 5m D 40cm
Cau 7: (De thi tot nghiep nam 2009). Mot chat dilm dao dong dieu hoa tren
true Ox theo phuong trinh x = 5cos(4;Tt) (x tinh bSng cm, t tinh bSng s) Tai
thai dikm t = 5s, van toe cua chdt diem nay c6 gia tri bSng
A 5cm/s B 20;Tcm/s
C.-20;rem/s D Oem/s
Cau 8: Mot chat diSm dao dong dieu hoa tren true Ox theo phuong trinh x =
4eos(47rt) (x tinh bing cm, t tinh bang s) G6e toa dp tai vi tri can bang Do
Ion van t6c cua chk dikm nay khi vat qua vi tri can bang
A 16;r m/s B 4;rcm/s
C 16 ;r cm/s D 8;rem/s
Cau 9: Mot vat dao dong dieu hoa vai phuong trinh x = 6cos(4;7?)cm, gia
toe cua mpt vat tai thai diem t = 5s la:
A -947,4cm/s^ B 947,4cm/sl
C 0 D 974,5cm/sl
Cau 10: Mot chat di6m dao dpng dieu hoa vai chu ky 0,5;r(s) va bien dp
2cm Chon goc toa do tai vi tri can bang, \ky = 10 Gia toe cua chat
diem tai vi tri c6 li do Ian nhat eo dp Ian
A.4cm/sl B 16cm/sl C 32cm/sl D 0,5cm/sl
Cau 1 1 : Vat dao dong dieu hoa vai van t6c c\rc dai la 20 ;T cm/s va gia t6c
cue dai la 4m/s^ LSy TT^ = 10 thi bien dp dao dong ciia vat la:
A 5cm B 10cm C 15cm D 20cm
Cau 12: (De t h i dai hoc nam 2 0 0 9 ) Mpt vat dao dpng diSu hoa c6
phuong trinh x = Acos(cot + 9) Gpi v va a Ian lupt la van toe va gia toe cua
vat H? thiie dung la:
Cau 13: Mpt vat nho dao dpng dieu hoa vofi phuong trinh l i dp
X = Scos (107rt)(x tinh bang em, t tinh bang s) Khoang cdch tir vj tri can
bang den vi tri ma van t6c c6 dp Ian 40;i cm/s la •
A ±5cm B.±3cm C 3em D ±12cm Cau 14: Mpt vat nho dao dpng dieu hoa vai phuong trinh l i dp :t = Scos (107rt),(x tinh bang cm, t tinh bang s) G6c tpa dp tai vi tri can bang
Dp Ian v ^ toe cua vat khi v$t c6 li dp 4cm la
A SOTT cm/s B 3n m/s
C 60n cm/s D 6n cm/s
Cau 15: Mpt dao dpng dieu hoa tren quy dab dai 40 cm Khi a vj tri x =
10 cm v$t C O van t6c ZOTTVS cm/s Chu ki dao dpng cua vat la:
b Pha ban dau tp: (phirmg trinh dao dgng: x = Acos^Oit + (p))
Goc thai gian: t = 0
Vat qua vi tri x = X Q : COSO) = — , A Chieu duomg: v > 0 ^ sincp < 0; chieu am: v < 0 -> sincp > 0
c Co cp = > tr^ng thai ban dau (vgt & dau va dt chuyen theo chieu nao) x(t 0) xo '\c thai gian liic vat qua X Q va theo chilu
v(t = 0) =vo J duomg (vo > 0) hoac theo chilu am (vo < 0)
Trang 6CHlfdNGI: DAB g p G CdHQC WAT It 12-TOM TAT lY THUYgl VA BAI TAP TRAC BEHlgM-TAPI tfAT LY 12 - TJM TAT IX THUYfT VA BAI TAP TRAC H6HIEM - TAP 1
Chu y:
• Trong / T vat di dugc quang duomg 4A
• Trong vat di dugc quang duomg 2A
• Trong vat di dugc quang ducmg hkng A neu xuSt phat tir vi
tri bien hoac vi tri can bSng
• Trong i T quang duomg dai nli4t ma vat di dugc la A
• Trong - T quang duomg ngSn nhat ma vat di dugc la A
Bai tap mau:
B a i l : Mot vat dao dgng diSu hoa c6 phucmg trinh x = 4cos(107rt +1) (x
tinh bang cm va t tinh bang s)
a Tai thai diem t = 0, vat chuyen dgng nhu the nao ?
b Tinh thai gian ngSn nhat U tu luc t = 0 dgn khi vat di dugc
quang duong 4cm
c Sau khoang thai gian ngSn nhat la bao nhieu d l vat c6 l i dg x= -2cm
d Trong khoang thai gian 5s kk tir luc t = 0 vat di dugc quang
duong la bao nhieu?
e Tinh s6 Mn vat qua l i dg x = 2cm trong khodng thai gian 2s kg
tvr luc t = 0
CHtftfUE 1: B A O D Q M G C K H Q C
Giai: x = 4cos (lOnt +1) cm
a t = O.Xf) = Ovkvo = -AOncm/s < 0: Vat qua v} tri canbSng
theo chieu am (ngugc chieu duomg)
h s = A = 4cm => Vat di tir vi tri can bang den v i tri bien
la 10 X 2 = 20 (trong 1 chu ki chat diem qua VTCB hai Ian)
Bai 2: Xac djnh pha ban dau (p trong cac truang hgp sau (Goc tga dg tai
vi tri can bang)
a G 6 C thai gian luc vat qua vi tri can bang theo chidu duang
b G 6 C thai gian luc vat qua vi tri can bang theo chieu am
c Goc thai gian luc vat dang a vi tri bien duang
d Goc thofi gian luc vat a vi tri bien am
e Goc thcri gian luc vat qua vj tri ^ va chuygn dgng cung
Cau 1: Bi6u thuc l i dg theo thai gian ciia mgt vat dao dgng diSu hoa la x =
Acos (at + (p) Chgn dieu kien ban d i u nhu thS nao d l phuomg trinh cua no
CO dang dan gian la x = Acos {(oi)
A Goc tga dg trung voi vj tri can bang
B t = 0 vat qua vi tri can bang va dang chuyen dgng theo chihu duong
C t = 0 luc vat bat dau chuyen dgng tu bien duomg
D t = 0 vat qua v i tri can bang va dang chuyen dgng ngugc
chieu duong
Trang 7CHIfdNG 1 : DAB flflNE Cfl HgC V A T lY 1 Z - TDM T A T LY THUYfT V A B A I T A P T R A C H G H I E M - T A P I
Cau 2: Vat dao dpng dieu hoa c6 quy dao la 2cm, liic t = 0 dugc chon la luc
qua chu di qua v i tri c6 l i dp x = 0,5cm va dang chuyen dgng theo chieu
duong Pha ban dhu cua vat la:
3 6 2 3
Cau 3: (De thi cao dSng nam 2009) Mgt chat d i l m dao dong dieu hoa c6
phuong trinh van t6c la v = 4;rcos2;rf(cm/s) Goc tpa dp a vj tri can bang
M6c thai giandugc chon vao luc chat diem c6 l i dp va van toe la:
A x = 2cm;v = 0 B x = 0; v = 4;rcm/s
C. X = -2cm; v = 0 D x =0; v = ATT cm/s
Cau 4: Mot con \hc 16 xo dao dong theo phuang ngang vai phuang trinh:
(cm) Thai gian ngin nhat tir luc t = 0 den thai diem vat
Cau 5: Mot con iSc 16 xo dao dong diSu h6a vai phuang trinh x =
4 cos(47rt) (cm) Quang duong vat di dupe trong thai gian 3s ke tir liic t = 0 la
A 16cm B 3,2m C 6,4cm D 0,96m
Cau 6: Mot vat dao dong d'lhu h6a vai phuang trinh x = Acosnt (cm) G6c
tpa dp tai vi tri can bang Thai gian ngin nhat de vat di tir vi tri bien vh v i tri
can bang la:
A 2s B Is C.0,5s D 0,25s
Cau 7: (De thi cao dang nam 2009) Khi noi vh mot vat dao dpng diSu hoa
CO bien dp A va chu ky T, vai m6c thai gian t = 0 la luc vat a vi tri bien,
phat bieu nao sau day la sai:
A Sau thai gian T/8, vat di dupe quang duong 0,5A
B Sau thai gian T/2, vat di dupe quang duong 2A
C Sau thai gian T/4, vat di dupe quang duong A
D Sau thai gian T, vat di dupe quang duong 4A
Cau 8: Mot vat dao dpng dilu h6a vai chu k i T Neu chpn goc thai gian
t = 0 luc vat qua vi tri can bang, thi trong nua chu ki dau tien, van toe cua
vat bang khong a thai diem
A T/4 B.T/2 C T D 3T/4
CHIflflllB 1 : DAO OfiNG Cd HQC
Cau 9: Mpt con 15c 16 xo c6 dp cung k =100N/m, vat nang khoi luong
m = 250g, dao dpng d i l u h6a vai bien dp 4cm hiy to = 0 luc vat a vi trf
bien thi quang duong vat di dupe trong thai gian 7r/40 (s) dau tien la
A 12cm B 8cm C 4cm D 24cm
Cau 10: Thai gian ngSn nhSt de mpt vat dao dpng dieu h6a vai phuang
trinh x = Acos(;rt) cm di tir vj tri xi = — den vj tri X2 = A la:
• Mgt Id xo CO dQ cung k, rriQt dau dirfrc treo vao rngt diim c6 dink
ddu con Igi treo vgt c6 khSi luQng m Bo qua khoi hf(mg cua Id xo
• Tdn sd goc, chu ki, tdn sd:
4t Con l i e 16 xo treo thkng dung
(Goc tQa do tai vj tri can bang, chieu duomg huangxuSng)
^ Chi^u dai cua 16 xo khl v^t a vi tri can bang: = /Q + ^
^ Chieu dai cua 16 xo khi vat a vj tri x bat k i : |/ = /o+A/ + x
Trang 8CHKdMG 1: DAO OQNGCdHOC V A T LY 12 - TtM TAT LY THIIYgT V A BAI T A P TBAC NGNIEM - 1 * ^ 1
^ Chieu dai cue dai:
Chieu dai toi thieu: mm 0
(1) (2)
T u ( l ) v a (2): / _ ax ^min
* ~ 2 Chu y: Cac cong thiic tren dSu ap dung cho con lac 16 xo nam ngang
nhung A/ = 0
B a i t a p m a u : Mot con iSc 16 xo c6 chiSu dai ban dSu h = 20cm treo
thing dung, dau dual g i n vat c6 kh6i lucmg m =100 g, dp cung k = 100
N/m LSy g = lOm/s^, TT^ « 10 Bo qua mpi l\rc can
a Tinh dp bien dang cua 16 xo va chieu dai cua 16 xo khi vat a vj
tri can bSng
b Xac dinh tan so goc, chu ki, tan so
c Tir v i tri can bSng keo vat xu6ng theo phuorng thing dung mot
doan 5cm r6i tha nhe Goc tpa dp tai vj tri can b3ng, chilu
ducmg la chieu keo vat, Goc thoi gian luc tha vat V i l t phuomg
trinh dao dpng cua v^t nang
d Tinh chieu dai cua 16 xo khi vat c6 v ^ toe 40Tr cm/s va dang a
phia tren vi tri can bang
e Tinh chieu dai c\rc dai, chieu dai cue tieu cua 16 xo
Giai: m = 100^ = 0,1^5, = lOON/m, = 20cm
a Ai = ^ = ^ = 0,01m = \cm,U = lo + M = 21cm
h 0) = k
m ^ = IOTT rad/s, T = 0,2 s,f = SHz
c Phuong trinh dao dpng: x = Acosicot + (p)
A = 5cm, w = IOTT rad/s, (p = 0-* x = 5 cos(107rt) cm
d A^ = x^+-,=^x = ± A^-^= ±3cm V i vat n i m tren vj
tri can bSng nen x = -3 cm
lupng m va 16 xo c6 dp cung k khong doi, dao dpng dieu hoa N6u kh6i
lugmg m = 200 g thi chu k i dao dpng cua con lie la 2 s Da chu k i con l i e la
1 s thi khoi lupnng m bftng
A 200 g B.lOOg C 5 0 g D 800 g
Cau 3: Mpt con l i e 16 xo gom vat c6 kh6i lupng m va 16 xo c6 dp cung k,
dao dpng dieu h6a N I U tSng dp cung k len 4 l i n va giam khoi lugrng m di 4 Ian thi tan so dao dpng cua vat se
A tang 2 l i n B giam 2 ISn
Cau 5: Khi g i n qua nang mi vao mpt 16 xo, no dao dong vai chu ky Ti = 1,2s
Khi gan qua nSng m 2 vao 16 xo do, no dao dpng vai chu ky Tj = 1,6s Khi g i n
dong thai mi v^ m 2 v^o 16 xo do thi dao dpng cua chung la:
A 1,4s B 2 s C.2,8s D.4,0s
CSu 6: Mpt con lie 16 xo c6 kh6i lupng m = 0,4kg g i n vao dSu 16 xo c6 dp
cung 40N/m Nguai ta keo qua nang ra khoi vj tri can bing mpt doan 4cm roi tha nhe cho n6 dao dpng Van t6c c\rc dai cua vat nang la:
A 160cm/s B.80cm/s C.40cm/s D.20cm/s CSu 7: Mpt con l i e 16 xo gom mpt qua n3ng c6 khoi lupmg 1kg va mpt 16
0 CO dp cung 1600N/m Khi qua nSng a vi tri can bing, nguod ta truySn cho mpt van t6c ban dau bing 2m/s Bien dp dao dpng cua qua nSng la
A 5m B.5cm C 0,125m D 0,125cm
Trang 9CHlflfHei:DAOD()HECtfHqC WAT i t K - TJM TAT I * THDYfT VA BAI TAP THAC WEHigM - W 1 vAl LY 12 - TOM TAT LY THUYgT VA BAI TAP TBAC HEHIgM - TAP 1 CHtftfHGlrBAO flOWGCUHqC
Cau 8 : (De thi cao ding nam 2009) Mpt con idc 16 xo treo thSng dung dao
dong dieu hoa voi chu ky 0,4s Khi vat a vi tri can bang, 16 xo dai 44cin
Lay g = ( m/s^) ChiSu dai t\ nhien cua 16 xo la:
A 36cm B 40cm C 42cm D 38cm
Cau 9: Mpt con idc 16 xo treo thing dung va dao dpng dieu hoa voi tan s6
f = 4,5 Hz Trong qua trinh dao dpng chieu dai cua 16 xo bien thien tir 40 cm
den 56 cm Lay g = 10 m/s^ Chigu dai tu nhien cua 16 xo la
A 46,8 cm B 48 cm C.40cm D 42 cm
Cau 10: Mot vat dao dong dieu hoa khi qua vi tri can bang v§t c6 van t6c
V = 20 cm/s Gia toe e\rc dai cua vat la amax = 2m/s^ Chgn t = 0 la luc vat
qua vi tri can bang theo chieu am cua tr\ic to? dp Phuorng trinh dao dpng
cua vat la:
A x = 2cos(10t) em B x = 2eos(10t + 7c) em
C.x = 2eos(10t-7i/2)em D x = 2cos(10t + 7i/2) cm
V A N D E 4: D O N G NANG, T H E N A N G V A C O N A N G
Bai tap mau: Mot con lac 16 xo treo vai vat nang m = lOOg dang dao
dong dieu h6a voi phuang trinh x - 2cos(10nt)cm G6c thi nang va g6c tpa dp tai vi tri can bang Lay g = n^ = 10 m/s^ Tinh:
a Dp cung k ciia 16 xo
b Tan so cua dpng nang
c Co nang cua con lac
• Khi dQng ndng tang thi the ndng giam va ngu(rc Igi, nhimg tSng
dQng nang va thi nang ludn khong doi, ca nang bao toan
• Tdn s6 dgng nSng = tdn so thi ndng == 2 X tan s6 dao dgng
• Cic sau khodng thai gian — thi dpng nang bSng thi nang
4
d The nang va dpng nang khi t = 1 s
e Dpng nang cua con lac khi vat nang qua vi tri c6 li dp x=lcm
f Ti s6 dpng nang va thi nang khi vat c6 van t6c v = lOn cm/s
g Khoang each tu vi tri can bang din vi tri c6 li dp ma dpng nang
bang 3 Ian the nang
Giai; m = 100^ = OMg.x = 2cos(10nt)cm
Cau 1: Mpt vat dao dpng digu hoa theo phuang trinh: x =
lOcos (4nt + n/2) cm Dpng nang cua vat b i k thien vai tan s6 la
A.4Hz B.2Hz C IHz D 6Hz
Cau 2: Mpt vat dao dpng dieu hoa theo mpt tryc e6 dinh (m6c thi nang a vi
tri can bang) thi
A dpng nang cua v$t e\ie d^i khi gia toe cua vat eo dp Ian c\re dai
B khi vat di ti^ vi tri can bang ra bien, v ^ t6c va gia t6e cua vat luon cung dau
C khi 6 vi tri can bang, thi nang cua vat bang ca nang
D li dp bang kliong khi dpng nang bang ca nang
17
Trang 10CHtftfHG 1: DAO DQIIB Cfl HpC V*T LY n - T U M TAT it THBYfT W A thl T<P TBAC HBBltW - T jp 1
Cau 3: Mpt con lie 16 xo gom vat nSng khoi lugrng m = 0,2kg va mpt 16 xo
C O do cung k = 50N/m Keo vat khoi vi tri can bang 2cm roi truyen cho vat
mot van toe dku ISVScm/s Co nang dao dong cua vat la:
A 212,5J B 0,02125J C 425J D 0,0425J
Cau 4: (De thi cao dSng nam 2008) Chdt di6m c6 khoi lugng mi = 50g dao
dong di6u h6a quanh vj tri can bang cua no voi phuomg trinh dao dpng xi =
cos{57a + Tt / 6} cm Chat dilm c6 kh6i luomg m2 = lOOg dao dpng dim h6a
quanli vi tri can bang cua no voi phuong trinh dao dpng X2 = 5cos{nt-n/6)
cm Ti so CO nang trong qua trinh dao dgng dieu hoa ctia chat diem mi so
voi chat di^m m2 bang:
A 2 B 1 C 1/5 D.0,5
Cau 5: Mpt con lac 16 xo gom 16 xo c6 khoi lugrng nho khong dang kg,e6 dp
cumg k = 40N/m gan voi qua cau c6 kh6i lupng m Cho qua eSu dao dong vol
bien dp 5cm Dong nang cua qua cau a vi tri ung voi li dp 3cm la:
A 0,018 J B.0,5J C 0,032 J D.320J
Cau 6: Mpt con lac 16 xo dao dpng theo phuong ngang vai bien dp A Moc
the nang a \\i can bang Li dp vat khi dpng nang cua vat nho horn the nang
ctia 16 xo hai Ian la:
A ;c = ±Ayf3 B x
2
Cau 7: (De t h i cao dSng nam 2010) Mpt con lac 16 xo gom vien bi nho
16 xo nhe c6 dp cung 100 N/m, dao dpng dieu h6a voi bien dp 0,1 m Moc
thg nang a vj tri can bang Khi vien bi each vj tri can bang 6 cm thi dpng
nang cua con lac bang
A 0,64 J B.3,2mJ C.6,4mJ D 0,32 J
Cau 8: (De thi dai h^c nam 2009) Mpt con lie 16 xo g6m mpt 16 xo nh? va
mpt vat nho dao dpng dieu h6a theo phuong ngang voi tan so g6c lOrad/s
Biet rang khi dpng nang va the nang (moc d vj tri can bang cua vat) bang
nhau thi v ^ toe cua v^t c6 dp Ion bang 0,6m/s Bien dp dao dpng cua con
Cau 9: (De t h cao dSng nam 2010) Mot vat dao dpng dku hoa dpc theo
J'' n o / ^^'^ " ^ " ^ " ""^^ ^ ^ " g - ^ th^' ^'^"^ ^9 16n van t6c cua vat bang 50% van toe cue dai thi ti so giua dpng nang va ca nang cua vat la '
Cau 10: Mpt con lac 16 xo dao dpng d i k h6a Khi dpng nang bang 3 \h
the nang (moc 6 v i tri can bang cua vat) thi l i do cua vat la 2cm Li do
vat khi dpng nang bang the nang va gia t6c nh^n gia tri ducrng la
B -2>/2cm
an cua
A. 2 cm C. -2 cm D 2V2 cm
VAN D E 5: L ^ C DAN HOI - L ^ C K E O V E
• <//,(min) =k{Al-A) niu Al > A
i Lye dan hoi: F^=k(Al+x)
- XetdQidm: F^^^=k(Al + A)
^ * { m i „ ) = 0 niu Al<A
* Lye keo ve: F,=-kx = -kA cos {cot + <p)
- Xet dQ Ian: Luc vat qua vj tri can bdng: x = 0 - > = 0
Luc vat a vf tri bien: x = ±A-^F,, ,=kA
Chiiy: Doi voi con lac 16 xo nam ngang A/ = 0 -» F^^ = F^
\ai t a p 5;
:au 1: Mpt con lac 16 xo kh6i lupng vat nang m = lOOg, dang dao dpng diku
theo phuomg ngang voi phuong trinh: A: = 10 cos (st + ^) cm Dp Ion
lire dan hoi tai thai diem t = 7t/5 s la:
A 0,216N B 21,6N C 12,6N D.216N
;9
Trang 11CHIfflNGI: DAODtNGCdHQC VAT lY 1 2 - TdM TAT I V THBYfT VA BAI TAP THAC W H I E M - TAP 1
Cau 2: (De t h i tot nghiep nam 2009) Mot vat nho dao dong dihu hoa theo
mot true CO dinh Phat bieu nao sau day dung?
Ạ Quy dao chuyen dong cua vat la mot doan thing
B Luc keo ve tac dung vao vat khong doị
C Quy dao chuyen dong ciia vat la mot duomg hinh sin
D L i dO cua vat ti 1? vdi thai gian dao dong
Cau 3: Mot chat dilm c6 kh6i lugng m = 50g dao dpng diSu hoa tren doan
thang 8cm vai tan so f = 5 Hz Khi t = 0 chat diem qua vi tri can bang theo
chieu duang Goc toa do tai v i tri can bang Lay TT^ = \ỌCi thai dilm
1
/ = — s, l\rc keo ve c6 do Ian:
60
Ạ I O N B. V3 N C I N D loVsẬ
Cau 4: Con lac 16 xo dao dong theo phuang ngang vai bien dp 8cm va chu
ki T = 0,5 s, khoi lucmg cua vat la 0,4kg, (lay = 10 Gia tri cue dai cua
lire dan hoi tac dung vao vat la
Ạ 512N B 5,12N C 2 5 6 N D 2 , 5 6 N
Cau 5: Mpt con lac 16 xo gom vat nSng kh6i lugng m = lOOg va 16 xo c6
do cung k = 40N/m treo thing dung Cho con l i e dao dpng vai bien dp
3cm Lay g =10m/s^ Luc dan hoi cue dai tac dung len vat c6 dg Ion:
Ạ 2,2N B 0,2N C 0,1N D I N
Cau 6: Con lac 16 xo dao dpng dieu h6a theo phuang thing dung c6 nSng
lugng dao dgng 2.10'^J, lire dan hoi cue dai cua 16 xo 4N Lye dan hoi cua
16 xo khi vat a vi tri can bing la 2N Bien dg dao dpng se la
Ạ 3cm B 4cm C 5cm D 2cm,
Cau 7: Mot con lac 16 xo treo thing dung dugc kich thich cho dao dgng
dieu hoạ Thai gian qua c i u di tir vi tri cao nhat den vi tri thip nhit la 1,5s
va ti so giura dg Ian ciia l\rc dan hoi 16 xo va trgng lugng qua cau g i n a dau
con lie khi no a \\i thap nhit la ^ L i y g = 7t^m/s^ Bien dp dao dgng cua
con ac la:
Ạ 5cm B 4cm C 3em D 2cm
Cau 8 MOt 16 xo c6 dg cung k = 20N/m treo thing dung Tir vj tri can bing,
dira vat len mpt doan 5cm r6i buong nh? L\rc keo vk c6 dg Ian c\rc dai 1^
Ạ 3 N B I N C lOON D ION
20
K^T LY 12 - TOM TAT LY THUYgj VA BAI TAP TRAC WGHIEM - TAP 1 CHI/KNG1: DAO DONG CK HQC
VAN D E 6: CON L A C DON
4* Tan so goc, chu ki, tan so:
2n^ I
4 Co-nang: W = - mgloQ UQ la bien do goc (rad) ,
Moi lien he giúa coil lac 16 xo va con lac don:
X = la A = IUQ
Dao dong ciia con lac don k h i chiu tac dung cua luc la:
Chu ki dao dgng mai:
g'la gia toe trong trir&ng bieu kien: g' = g + a neu F g
g' = g + a neu F It g g' = g - a niu F g g' = -yjg^ + niu Fig
F Id luc dien tru&ng: F = qE
Bai tap mau: Mot con lie dan c6 chiSu dai day treo / = I m va kh6i lugng
vat nang la lOg Keo con l i e dan ra kh6i vj tri can bang vai goc lech 8° roi tha nhẹ Bo qua moi ma sat va chuyen dgng cua vat nang la dao dong dieu hoạ Lay g = 9,8 m / s l
ạ Tinh chu k i dao dpng
b Tinh ca nang cua con lac
c Tinh goc lech cua day treo va phuang thing dumg khi dgng nang bang
ba Ian the nang
d NSu giam dp dai cua con lie xu6ng mot doan 20cm thi trong 1,8 phut
vat thuc hien dugc bao nhieu dao dong
ẹ Vai / = Im, tinh lai chu ki cua con lie trong cac truang hgp sau:
Trang 12CHaOfNG 1: DAO D9N6 tSm yATLYIZ-TiMTATlYTHUYgTyABAlTAFTRAc HGHlf M - TAP 1 W U « - TIJM TAT i t THUVgl »A BAI TAP TBAC IISHIEM - TAP 1 GHlTlfNG 1: DAO DQNG CO HQC
• T H I : Treo con l i e trong rngt tang thang may di len nhanh dan deu
vdi gia toe a = 2m/s^
• T H 2 : Treo eon lae trong mot tran xe, biet xe dang tang t6c voi gia
toe 2m/s^
" rH3: Thay vat nang bang mpt vien bi kim loai eo cung kh6i lugng
I'hung mang di?n tieh q = +3,2 lO'^C, sau do dat con lac trong mot dien
ti-ucmg deu huong len thSng diing va c6 do Ion E = 4.10^ V/m
Giai: / = l m , m = lO^f = O^Olfc^, = 8° = 0,14 rad
Cau 1: Mot con lac dorn dao dpng di^u hoa tai nori c6 gia t6c trpng truomg
g = 1 Ow / 5^ CO tan s6 0,5Hz LSy ;r ^ = 10 Chieu dai cua con lac la
A 1cm B 100cm C 10cm D 10m
Cau 2: (De t h i tot nghiep 2007) Tai mot nori xac dinli chu k i cua con lie
dorn dao dpng dieu hoa thi ti 1? vai:
A ChiSu dai con lac B Gia t6c trQng truong g
C can bac hai cua chieu dai D Can bac hai cua gia t6c g
Cau 3: Mot con lac dan c6 chu ky 1,5s khi no dao dpng a nai tren Trai Dat
Tinh chu ki cua con lac nay khi ta dua no len Mat Trang, biet ring gia t6c
trong truomg cua mat trang bang 60% gia t6c trong truomg tren Trai DSt:
A 2,5s B 3,75s C 1,94s D 0,54s
C*Su 4: Tai mpt nai c6 gia toe trpng truong g, mpt con lac dan c6 chieu dai
/, dao dong vai tan so 8Hz Mpt con lac dan c6 chieu dai h dao dpng vai tan
s6 6 Hz Con lac dan c6 chieu dai / = / i
A 2,4 Hz B 5 Hz
+ h dao dpng vai tan so f bang
C 4,8 Hz D 1,4 Hz 5: (De t h i cao dang nam 2010) Tai mot nai tren mat dat, con lac dan
CO chieu dai i dang dao dpng dieu hoa vai chu ki 2 s Khi tang chieu dai cua con lie them 21 cm thi chu ki dao dpng deu cua no la 2,2 s Chieu dai i bang
A 2 m B I m C 2,5 m D 1,5 m
Cau 6: (De t h i dai hoc 2009) Tai nai c6 gia t6c trpng truong 9,8m/s^, mot
con lie dan va mot con lie 16 xo n i m ngang dao dpng dieu hoa vai cung t i n s6 BiSt con lie dan c6 chigu dai 49cm va 16 xo c6 dp cung lON/m Kli6i luong vat nho cua con lac 16 xo la:
A 0,125 kg B 0,500kg C 0,750kg D 0,250kg CSu 7: Treo con lac don vao tran mot oto tai nai c6 gia toe trpng truong g = 9,8 m/s^ Khi oto dung yen thi chu ki dao dpng dieu hoa cua con lac 10 s NSu oto chuyin dpng thing nhanh d i n deu tren duomg n i m ngang vai gia t6c 3 m/s^ thi chu k i dao dpng dieu h6a ciia con lie xap x i bang
A 2,06 s B 7,28 s C 9,77 s D 6,02 s
Cau 8: Mot con lac dan gom mot day treo c6 chieu dai 0,5 m, vat nang c6
kh6i luang 40g mang dien tich q = -8.10"^ C dao dpng trong dien truang deu c6 phuong thang dung c6 chieu huomg len va c6 cuang dp E = 4000 V/m, tai nai CO g = 9,8 m/s Chu ki dao dpng cua con l i e la:
A 1,05 s B 2 , l s C 1,5 s D 1,6 s
Cau 9: Tai nai c6 gia toe trpng truang g, mot con lac dom dao dong dieu h6a vai bien dp goe ao BiSt khoi luong vat nho cua con lie la m, chieu dai day
treo la (., moe the nang a vi tri can bing Ca nang cua con lac la
A ^mgeal- B mg^tto C
\mgial-4
D 2mg^a^
Cau 10: Tai nai c6 gia toe trpng truang 9,8 m/s^, mot con lie dom dao dpng dieu hoa vai bien dp goc 6° B i l t kh6i lupmg vat nho cua con lac 190 g va chigu dai day treo I m Chpn m6c the nang tai vi tri can bing, ca nang cua con lac xap x i bang
A 6,8.10-^ J B 3,8.10-^ J
C 5,8.10"^ J D.0,01J
Trang 13CHKKNB 1 : DAO DQNG Ctf HPC WAT I t 12 - TfiM TAT LY THUYfT VA BAI TAP TRAC WEHlgM - TAP 1
V A N D E 7: T O N G HOfP D A O D Q N G
Cho 2 dao dong dieu hoa cung phuong, cung tan so:
Dao dong 1: = ylicos (cot + (p^) Dao dong 2: X2 = v 4 2 C 0 S (cot + (P2)
Dao dong tong hop: x = Acos((jL)t + cp)
4 Bien do dao dpng tong hop:
A = ^JA^ + Al + 2A^ ^ 2 cos A ^ Acp = ~ t^O lech pha
•4 Pha ban dau cua dao dong tong hop dugc xac dinh:
tan^ = sin (p^ + Aj sin (p^
y i , C 0 S ^ , +A2C0S(Pj
Cac truotig hoD dac biet;
' + = 0 : Hai dao dong ciing pha thi dao dong t6ng hop c6 bien do
cue dgi: A = A^ax = A^ + A2
+ Acp = ±7r: Hai dao dong ngu(xc pha thi dao dong t6ng hop c6 bier
dQ cue tiiu: A = Amin = l^i-Azl
+ A ^ = ± y : Hai dao dpng vuongpha: A = ylA\ A
C h u y : A^^ < A <
Bai tap 7
Cau 1: MQt vat tham gia vao hai dao dpng dieu hoa cung phuong, ciing tan
s6 thi:
A. Dao dong tong hop cua vat la mot dao dong dieu hoa cung tan so, c6
bien do phu thuoc vao hi?u so pha cua hai dao dong thanh phan
B Dao dong tong hop cua vat la mot dao dong tuan hoan cung tan so
C Dao dong tong hgp cua vat la mpt dao dong di6u hoa cung tan so,
cung bien do
D. Dao dong tong hgp cua vat la mot dao dong tuan hoan cung tan so,
CO bien do phu thuoc vao hi?u s6 pha cua hai dao dong thanh phan
Cau 2: Chon cau dung Bien do dao dong tong hgp cua hai dao dong dieu
hoa cung phuong, cung tan so c6 gia tri
A. cue tieu khi hai dao dgng thanh phSn lech pha | •
B. c\rc dai khi hai dao dgng thanh phan cung pha
1/ATLY 1 2 - T 6 M TAT lY THUYfT VA BAI TAPTRAC W E H I E M - TAP 1 CHl/tfUe 1 : DAD flpHE COHQC
C bang tong bien do cua hai dao dong thanh phin
D. cue dai khi hai dao dong thanh phan ngugc pha
Cau 3: Mot vat thirc hi?n dong thofi hai dao dong dieu hoa cung phuong, ciing tan s6 c6 bien do Ian lugt la 8cm va 12cm Bien dg cua dao dgng t6ng hgp CO t h i la:
A 2cm B 3cm C 5cm D 21cm
Cau 4: (De thi tot nghiep nam 2009). Cho hai dao dgng diSu hoa cung
phuong CO cac phuong trinh Ian lugt la xi = 4cos n
Cau 5: Mot vat thuc hien d6ng thoi 2 dao dgng d i l u hoa cung phuong, theo
cac phuong trinh x i = 4sin(;7? + a ) c m va X2 = 4 Vs cos(;7f)cm Bien do dao
dong tong hgp dat gia tri:
A ^ B ^ C - ^ D ^
12 6 2 4
Cau 7: (De thi dai hoc nSm 2009) Chuyen dgng cua mgt vat la tong hgp
cua hai dao dgng dieu hoa cung phuong Hai dao dgng nay c6 phuong trinh
l^n lugt la x i = 4cos(l0/+ ;7-/4) cm va X2 = 3cos(l0/-3;r/4)cm Dg Ion
toe cua vat a v i tri can bSng la:
A 80cm/s B lOOcm/s C lOcm/s D 50cm/s
Cau 8: (De thi cao dSng nam 2010). Chuyen dgng cua mgt vat la tong hgp ciaa hai dao dgng dieu hoa cung phuong Hai dao dgng nay c6 phuong trinh
l&n lugt la X i = 3cos(10t) (em) va X2 =4sin(10/+—) (cm) Gia toe cua v^t c6
<10 lom c\rc dai bang
A 7 m/sl B 1 m/s^ C 0,7 m/sl D 5 m/sl
Trang 14CHtftfWei: DAB BOWG CI» HOC VAT LY 12 - T J M TAT LY THBYgT VA BAI TAP TRAG WEHltM - TAP 1
Cau 9: Hai dao dong dieu hoa cung phucmg c6 phuong trinh Ian lugt la Xi =
4cos(7rt) (cm) va X2 = Acos(7rt — ^ ) (cm) Dao dong tong hop ciia hai dao
dong nay c6 bien do la 4 Vs cm Gia tri cua A la
A 4cm B 3cm C 2cm D 4V2cm
Cau 10: Dao dong tong hop cua hai dao dong dieu hoa cimg phuong xi ~
4sin(107rt+—) cm va X2 = 2cos(107rt +7i) cm, c6 phuong trinh:
a Dao dong t^t dan:
• Dao dong tat dan la dao dong c6 bien do gidm dan theo thai gian
• Nguyen nhan: Do lire can
• S\ tat dan cua dao dong c6 khi c6 Igi, c6 khi c6 hai tuy theo muc
dich va yeu chx cu ihk
b Dao d^ng cu-ong birc:
• Dao dgajg cuong buc la dao dong cua vat do chiu tdc dung cua
ngogi tire cuang buc tudn hodn
• Dac diem:
- Dao dong cuong buc la dao dong dieu hoa
- Dao dgng cuong bite khi on dinh c6 tdn s6 bdng tan so cua luc
cuomg buc
- Bien do cua dao dong cuong buc khong chiphu thuoc vdo bien do
cua luc cuang bite, ma con phu thugc vdo cd tdn s6 cua ngogi
luc Khi tan so cua luc cuong buc cang gkn vai thn so rieng thi
bien do cua luc cuong buc cang Ion
c C^ng hirong:
• Dieu kien: Tan so rieng fo ciia h^ bdng tdn so ngogi luc f
• Dac diem: Bien dp dao dpng dat gia trj cue dai
VAT " - TiM TAT LY THUYfT tfA BAI TAP THAC WGHIEM - TAP 1 CHlfflNB 1 : BAD fljWGCItHqC
Rai tap 8;
CSu 1: (De thi dai hpc nSm 2009) Nhan dinh nao sau day sai khi noi vk
dao dong ca hoc t i t dan?
A Dao dong iii dhn c6 dong nang giam dhn con the nang bien
thien dieu hoa
B Dao dong tat dan la dao dong c6 bien dp giam dan theo thai gian
C Luc ma sat cang Ion thi dao dong tat cang nhanh
D Trong dao dong tat dan, ca nang giam dan theo thai gian
Cau 2: (De thi cao dang nam 2009) Phat bieu nao sau day la diing khi noi
vk dao dong tat d4n?
A Dao dong tat dan c6 bien do giam dan theo thai gian
B Ca nang cua vat dao dong tat dan khong doi theo thai gian
C Luc can moi truang tac dyng len vat luon sinh cong duang
D Dao dong tat dan la dao dong chi chiu tac dung ciia noi luc Cau 3: Chon cau tra lai sai:
A Dao dong tSt dan la dao dgng c6 bien do giam dan theo thai gian
B Dao dong cuang biic la dao dong dual tac dung cua ngoai luc
bien thien tuan hoan
C Khi cpng huang dao dong: thn s6 dao dpng ciia h? bang tan so
rieng cua he dao dong
D Tan so cua dao dong cuang buc luon bang tan so rieng cua h?
dao dong
Cau 4: Bien do dao dong cuong buc khong phu thuoc:
A Pha ban dau cua ngoai luc tuan hoan tac diing len vat
B Chu ky ngoai lyre tuan hoan tac dung len vat
C Tan so ngoai luc tuan hoan tac dung len vat
D H? so luc can ( cua ma sat nhat) tac dung len vat
CSu 5: (De thi tot nghi?p nam 2009) Dao dgng tat dan
A Luon CO hai
B Co bien do khong doi theo thai gian
C Co bien dp giam dan theo thai gian
D Luon CO Igi