Thiết kế bài giảng vật lý 12 nâng cao (tập 1) phần 1

Hay vie't cdng thiic xac dinh tdc dp gdc ciia vat d thdi diem t, phuang trinh chuyen ddng eiia vat rin, cdng thiic ddc lap vdi thdi gian trong chuyen ddng quay.. GV neu cac cau hdi gpi y

TRAN THUY H A N G HA D U Y £ N TUNG

NANG CAO

TAPMOT

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NANG CAO - TAP 1

NfiA XUAT BAN HA NOI

.ai not ddu

Thie't ke bai giang Vat li 12 nang cao dvroc viet theo chifdng

trinh sach giao khoa m6i ban hanh nam 2006 - 2007 Sach gidi thif u m6t each thi§'t ke bai giang VSt li nang cao theo tinh than doi mdi phifdng phap day - hoc, nham phat huy tinh tich ciTc nhan thiic cua hoc sinh

Ve noi dung : Sach bam sat noi dung sach giao khoa VSt li 12

theo chifdng trinh nang cao O moi tie't, sach chi ro muc ti§u ve

ki^'n thiic, ki nSng, c»c c6ng viec chuan bi ciia giao vi^n va hoc sinh, cac phtTOng tien ho trd giang day can thie't, nham dam bao chat Iifdng tufng.bai, timg tie't len Idp Ngoai ra sach co md rong,

bo sung them m6t sd' ndi dung lien quan tdi bai hoc bang nhieu hoat dong nham cung cS'p them tu" lieu d6 cac th^y, co giao tham khao vSn dung tuy theo do'i ttfdng hoc sinh tiing dia phiTdng

Ve phifdng phap day hoc : Sach diTdc tri^n khai theo hvrdng tich

cue hoa hoat ddng cua hoc sinh, lay cd sd cua moi hoat dong la nhiing viec lam cua hoc sinh dudi su" htrdng d i n , phvi hdp vdi dac trvmg mon hoc nhiT : thi nghif m, thao luan, thu'c hanh, nham phat huy tinh doc lap, tu" giac cua hoc sinh Dac bi^t, sach rat chii trong khau thu'c hanh trong timg bai hoc, ddng thdi ciing chi

ro tung hoat ddng cu thg cua giao vien va hoc sinh trong mdt tiS'n trinh day hoc, coi day la hai hoat ddng ciing nhau trong do

ca hoc sinh va giao vign la chu the

Chiing tdi hi vong cud'n sach nay se la mdt cdng cu thie't thUc, gop p h i n hd trd cac thiy, cd giao giang day mdn Vat li 12 trong viec nang cao hif u qua bai giang cua minh

Cac tac gia

CHi/ONG 1 DONG Ll/C HOC VAT RAN

- Hoc sinh hieu duoc khai niem vat rdn va chuyen ddng tinh tien cua vat ran la gi

- Hoc sinh hieu duoc khai niem toa dp goc (p

- Xay dung dupe cac cdng thiic tdc do goc co, gia tdc gdc y

- Nam viJng cac cdng thiic lien he giiJa tdc do gdc va tdc do dai, gia tdc gdc va gia

tdc dai ciia mot diem tren vat rSn

- Xay dung dupe cac phuong trinh ddng hpc ciia chuyen ddng quay

- Van dung dupe eac cdng thiic ciia chuyen ddng quay deu, quay bie'n d6i diu de

giai cac bai tap don gian

Ill - THifiT Kfi' HOAT D 6 N G DAY - HOC

Hoat d o n g cua hoc s i n h

Hoat dong 1

Kiem tra, chuan bi dieu' kien

xuat phat Dat van de

HS suy nghT ca nhan tim cau tra

Idi

HS nhan thiic dupe van de cua bai

hpc

Hoat d o n g 2

Tim hieu khai niem toa do goc

HS quan sat hinh ve 1.1 tren kho

gia'y AQ, suy nghT ca nhan tim eau

tra Idi

— Mdi diem tren vat vach mdt

dudng tron nam trong mat phang

vudng gdc vdi true quay, n

kinh bang khoang each tir di6m do

de'n true quay, tam ciia quy dao

nam tren true quay

- Mpi diem ciia vat deu quay duoc

cung mdt gdc trong cung mdt

khoang thdi gian

Tror giiip cua giao v i e n

GV neu cau hdi kiem tra kie'n thiie cu

- Neu khai niem vat ran

- Chuyen ddng tinh tien la gi ?

- Viet phuong trinh chuyen ddng cua vat chuyen ddng thing bie'n doi deu Viet cdng thiic van tdc cua vat dd

Dgt vdn de : 6 Idp 10, chiing ta da xac

dinh quy luat chuyfin ddng ciia vat ran chuyen ddng thang bie'n doi deu Bai hpc nay chiing ta di sau tim hieu va xac dinh quy luat chuyen ddng, tim mdi lien

he giOa eac dai lupng dac trung cho chuyen ddng quay cua vat ran quanh true CO dinh

GV neu cau hoi de HS tim hieu khai niem toa dp gdc:

- Xet.mdt vat ran bat ki quay quanh mdi

tmc Az t d dinh (Hinh 1.1 SGK) Hay

cho bie't dac diem ciia quy dao cua mdt di6m tren vat ran khi vat ran chuyen ddng

va gdc quay ciia cac diem tren vat ran?

Hoat d o n g cua hoc sinh

HS tie'p thu, ghi nhd

Hoat dong 3

Xay dung khai niem toe do goc

trung binh va tdc do goc tiic thdi

HS thao luan chung toan Idp j

- Dai lupng dac trung cho miic dp |

quay nhanh hay cham dupe xac :

dinh bang thuong so —^ • '

- De don gian, ta chi xet miic dp quay theo mdt chi6u va chpn chifiu duong la

chieu quay ciia vat, khi dd g)>0

GV neu cau hdi de HS xay dung khai niem tdc dp gdc:

- Khi vat rin quay, su bie'n thien theo

thdi gian ciia (p the hien quy luat

chuyen ddng quay cua vat rin Hay tim mdt dai lupng dac trung cho miic dp quay nhanh hay cham eiia vat rin Dai lupng dd dupe xac dinh nhu the nao ?

GV neu cae cau hdi gpi y:

- Trong chuyen ddng thing, dai lupng nao dac trung cho chuyen ddng nhanh hay cham ciia vat ? Dai lupng dd dupe xac dinh nhu the nao?

- Tuong tu, trong chuyen ddng quay, ta

cd the tim mdt dai lupng dac trung cho miic dd quay nhanh hay cham ciia vat rin dupe khdng ?

- 0 thdi diem t, toa dp gdc ciia vat la g)

0 thdi diem t +At, toa dp gdc ciia vat la

Hoat dong ciia hoc sinh Tror giup cua giao vien

HS thao luan chung toan Idp

- Tdc dp gdc tiirc thdi d mdt thdi

diem t duoc xac dinh bing gidi han

ciia ti sd —^ khi A / tien dan tdi 0

At

i^<P ,

co = hm hay ft) = ^ (t)

A/->0 At

- Don vi ciia tdc dp gdc la rad/s

(p + A(p, dai lupng dac trung cho miic

dp quay nhanh hay cham ciia vat rin dupe xac dinh nhu the nao ?

GV thdng bao:

- Dd chinh la tdc dp gdc trung binh j

C0f^J = cua vat rin trong khoang thdi

At gian At

- GV yeu cau HS xay dung cdng thiic

xac dinh tdc dp gdc tiic thdi va cho biet don vi cua tdc dp gdc

Hoat dong 4

Xay dung khai niem gia tdc goc

trung binh va gia tdc goc tiic thoi

HS thao luan chung toan Idp

- Dai lupng dac trung cho su bie'n

thien nhanh hay cham cua tdc dp

gdc dupe xac dinh bing thuang so

Aco

At

GV neu cau hdi de HS xay dung khai niem gia tdc gdc:

- Hay tim mdt dai lupng dac trung cho

su bie'n thien nhanh hay cham ciia tdc

dp gdc Dai lupng dd dupe xac dinh nhu the nao?

GV neu cac cau hdi gpi y

- Trong chuyen ddng thing, dai lupng nao dac trung cho sir bie'n thien nhanh hay cham ciia van tdc ? Dai lupng dd dupe xac dinh nhu the nao ?

- Tuang tu, trong chuyen ddng quay, ta

ed the tim mdt dai lupng dac trung cho

Hoat dong cua hoc sinh Trd giiip cua giao vien

HS thao luan chung toan Idp

- Gia tdc gdc tire thdi d mdt thdi

diem t dupe xac dinh bing gidi han

- Dan vi cua gia tdc gdc la rad/s

Gia tdc gdc tiic thdi ciia vat rin

quay quanh mdt true d thdi diem t

la dai lupng dac trung cho su bie'n

thien ciia tdc dp gdc d thdi diem

dd va dupe xac dinh bang gdi han

- O thdi diem t, vat cd tdc dp gdc la co

O thdi diem t + At, vat cd tdc dd gdc la (o + Ao) dai lupng dac trung cho sir

bie'n thien nhanh hay cham cua tdc dd gdc dupe xac dinh nhu the nao?

GV thdng bao:

- Dd chinh la gia tdc gdc trung binh

Ao) , , - , , , Yi^ = cua vat ran trong khoang thai

At gian At

- GV yeu cau HS xay dung cdng thiic

xac dinh gia tdc gdc tiic thdi va cho bie't don vi cua gia tdc gdc

GV yeu cau HS phat bilu khai niem gia tdc gdc

Hoat ddng 5

Xay dung cac phuong trinh dong

hoc ciia chuyen ddng quay

GV neu cau hdi de HS xay dung phuang trinh chuyen ddng ciia vat rin quay deu:

Hoat dong cua h9c sinh Trg giup cua giao vi^n

HS thao luan chung toan Idp

Phuong trinh chuyen ddng ciia vat

rin quay diu la : (p = (pQ + cot, trong

dd q)Q la toa dp ban dau luc f = 0

HS thao luan chung toan Idp

- Cdng thiic xac dinh tdc dp gdc

ciia vat chuyen ddng trdn bie'n doi

deu tai thdi diem / la :

co = coQ + yt

- Trong trudng hpp tdc dd gdc ciia vat

rin khdng doi theo thdi gian thi chuyen ddng ciia vat rin la chuyen ddng quay d6u Toa dp gdc ciia vat d thdi diem / dupe xac dinh nhu the nao ?

GV neu cac cau hdi gpi y

- Hay neu su tuang ling giOa cac dai lupng gdc trong chuyen ddng quay va cae dai lupng dai trong chuyen ddng thing?

- Viet phuong trinh chuyen ddng ciia vat chuyen ddng thing deu Tuong tu nhu vay chiing ta cd the vie't dupe phuang trinh chuydn ddng cho vat

chuyfin ddng quay diu nhu the nao ?

GV neu cau hdi de HS xay dung cac cdng thiic trong chuyen ddng quay bie'n doi deu:

- Trong trudng hpp gia tdc gdc ciia vat rin khdng doi theo thdi gian thi chuyen ddng ciia vat rin la chuyen ddng quay bie'n doi deu Hay vie't cdng thiic xac dinh tdc dp gdc ciia vat d thdi diem t, phuang trinh chuyen ddng eiia vat rin, cdng thiic ddc lap vdi thdi gian trong chuyen ddng quay

GV neu cac cau hdi gpi y:

- Viet cdng thiic xac dinh van tdc ciia vat chuyen ddng thing bie'n doi deu tai

thdi diem t, phuong trinh chuyen ddng

eiia vat va cdng thiic lien he giira van tdc, gia tdc va dp ddi

Hoat dong cua hoc-sinh

- Phuang trinh chuyen ddng quay

bie'n ddi diu :

1 2

<P = (Po + o)Qt+-rt^

- Cdng thiic ddc lap vdi thdi gian

0}^-Q)Q=2r{(p-q)Q)

Trong dd, ^Q' ^o 1^ ^^^ '^O goc va tdc

dp gdc ban dau tai thdi diem t = 0

HS tie'p thu, ghi nhd

Hoat dong 6

Tim hieu cac dac diem cua van

toe va gia toe ciia cac diem tren

vat quay

HS thao luan chung toan Idp

- Ne'u vat rin quay d6u thi gia tdc

cua mdt diem tren vat rin dupe xac

Trd g i u p cua giao vien

- Tuong tu cac cdng thurc cua chuyen ddng thing bie'n ddi deu, hay vie't cac cdng thiic cua chuyen ddng quay

GV thdng bao:

- Ne'u vat quay theo mdt chilu nhat

dinh va tdc dp gdc o) tang theo thdi

gian thi chuyen ddng quay la nhanh dan

ir>0)

- Neu tdc dp gdc giam dan theo thdi

gian thi chuyen ddng quay la cham din

ir<0)

GV neu cau hdi de HS tim hiiu cac dac diem ciia van tdc va gia tdc cua cac diem tren vat quay

- Ne'u vat rin quay khdng deu thi gia tdc cua mdt diem tren vat rin dupe xac dinh nhu the nao ?

GV neu cac cau hdi gpi y:

- Ne'u vat rin quay deu, gia tdc ciia mdt diem tren vat rin dupe xac dinh nhu the nao ? Cd the su dung cdng thiic gia tdc hudng tam da hpc d Idp 10 de xac dinh gia tdc eiia mdt diem tren vat rin dupe khdng ?

Hoat dong ciia hoc sinh

1

: :

- Neu vat rin quay khdng deu thi ;

mdi diem ciia vat rin cung chuyen \

ddng trdn khdng deu Khi dd vecto :

van tdc v ciia mdi diem thay doi :

ea ve hudng lin dp Idn Khi dd, ;

vecto gia tdc ciia mdi dilm cd hai

thanh phan :

Thanh phan Z^ cd phuong vudng •

gdc vdi V, dac trung cho sir thay ;

doi ve hudng ciia v, thanh phan •

nay chi'nh la gia tdc hudng tam ;

Thanh phan a, cd phuang ciia v, \

dac trung cho sir thay doi ve dp Idn •

- Dp Idn cua vecto gia tdc toan ;

phan dupe xac dinh ;

/ 2 2

a = ^a„+a, :

- Hudng ciia vecto gia tdc toan |

phan duac xac dinh vecto a hpp ;

vdi ban kinh OM gdc a, vdi i

tana = - ^ = ^ - ;

Trg giup cua giao vien

- Khi dd, gia tdc cua mdt dilm tren vat 1 rin dac trung cho tinh chat gi ciia van , tdc dai V ciia nd ?

- Neu vat rin quay khdng deu thi vecto j van tdc dai v cd dac diem gi ? i

- Cd thi sii dung hai thanh phin gia tdc

dl dac trung cho sir thay ddi ve hudng

va ve dp Idn cua vecto van tdc dai v dupe khdng ? Ne'u dupe, thi hai thanh phan cua vecto gia tdc dupe xac dinh nhu the nao ?

- Vecto gia tdc toan phin duoc xac dinh

; thdng qua hai thanh phan vecto gia tdc

; hudng tam va tiep tuye'n nhu the nao ?

i Hoat d o n g cua hoc sinh

1

1 Hoat dong 7

Cling cd bai hpc va djnh hudng

nhiem vu hoc tap tiep theo

Trg g i u p ciia giao vien

GV yeu cau HS lam viec vdi phieu hpc

;

tap-; - Yeu cau HS dn tap lai eac kie'n thii'c

; vl: mdmen lire, phuong trinh ddng lire

; hpc ciia chat dilm, y nghTa cua khdi

;lupng

PHIEU HOC TAP

Cau 1 Mdt canh quat dai 20cm, quay vdi tdc dp gdc khdng doi la 94 rad/s Tdc dp

dai cua mdt dilm d vanh canh quat bing

A 37,6 m/s B 23,5m/s

C.l8,Sm/s D 47m/s

Cau 2 Banh da cua mdt ddng co tir liic khdi ddng de'n liic dat tdc dp gdc 140rad/s

phai mat 2s Bie't ddng ca quay nhanh dan diu Gdc quay ciia banh da

trong thdi gian tren bing

A 140 rad B 70 rad

C 35 rad D 35 n rad

Cau 3 Mdt banh xe quay nhanh din diu quanh mdt true Liic t = 0 banh xe cd tdc

dp gdc 5 rad/s Sau 5s tdc dp gdc cua nd tang len de'n 7 rad/s Gia tdc gdc

cua banh xe la

C 2,4rad/s^ D 0,8rad/s^

Cau 4 Hai dilm M,, M2 tren mdt dTa CD, khoang

each tir tam cua dTa den hai dilm lan lupt la

2

/?,, 7?2 v^ R\=-R2- Cho dTa CD quay deu

quanh mdt true vudng gdc vdi tam ciia dTa

a) Ke't luan nao sau day diing khi ndi vl gdc quay

ciia hai dilm trong cung mot khoang thdi gian ?

PHUONG TRINH D O N G L U C HOC CUA VAT R A N

QUAY QUANH M 6 T TRUC c6 DEsJH

I - MUC TifiU

1 Ve kie'n thiic

- Xay dung dupe bilu thiic bilu diln md'i lien he giira gia tdc gdc va mdmen lire

ciia vat rin cd true quay cd dinh

- Dua ra eac du doan vl su phu thudc eiia mdmen quan tinh va thiet ke dupe phuang an thi nghiem kilm tra du doan

- Nim dupe khai niem mdmen quan tinh dd'i vdi mdt true cua vat rin

- Nim va van dung dupe phuang trinh ddng luc hpc cua vat rin quay quanh mdt true dl giai dupe mdt sd bai tap

2 Ve ki n a n g

- Van dung kie'n thiic vl mdmen luc da hpc d Idp 10 d l xay dung bilu thiic bilu

diln mdi lien he giira mdmen luc tac dung vao vat rin va gia tdc gdc

- Ren luyen kT nang dua ra cac du doan cd can cii

- Ren luyen kT nang thiet ke cac phuang an thi nghiem kilm tra du doan, thu thap

sd lieu, xu li sd lieu va dua ra ket luan

- Van dung phuang trinh ddng luc hpc ciia vat rin quay quanh mdt true de giai mdt sd bai tap

II - CHUAN BI

Giao vien

- Bd thi nghiem khao sat chuyin ddng tinh tien - chuyin ddng quay ciia he vat

- Ve bang 2.1 vao giay kho AQ

Hgc sinh

- On tap lai kie'n thiie vl mdmen luc, phuang trinh ddng luc hpc ciia chat dilm, y

nghTa ciia khd'i lupng

III - THlfiT Kfi' HOAT DONG DAY - HOC

Hoat dgng cua hgc sinh

Hoat dong 1

Kiem tra, chuan bi dieu kien

xuait phat Dat van de

HS suy nghT ca nhan tim cau tra Idi

- Tir bilu thire tinh mdmen cua lire :

M - F.d, suy ra tac dung lam quay

canh cira ti le vdi tich dp Idn ciia

luc tac dung va canh tay ddn cua nd

- Bilu thiic ciia dinh luat II Niuton

Trg giiip cua giao v i e n

GV neu cau hdi kilm tra kien thiic cu:

- Tac dung lam quay canh ciia phu thudc vao yeu td nao ? Bilu thiic toan hpc nao bilu thi dilu dd ?

- Viet bilu thiic ciia dinh luat II Niu-ton

Dgt vdn de : Trong chuyin ddng ciia

cha't dilm, giiia gia tdc cua chit dilm va lire tie dung cd mdi lien he dupe diln ta bing dinh luat II Niu-ton Trong chuyin ddng quay cua vat rin, gia tdc gdc va mdmen luc cd mdi lien he vdi nhau nhu the nao ?

Hoat d g n g cua hgc s i n h Trg giiip cua giao v i e n

Hoat d d n g 2

Tim mdi lien he giua gia tdc gdc

va mdmen luc

HS suy nghT ca nhan, sau dd thao

luan chung toan Idp

O - ^ T,

Luc F, gay ra gia tdc tie'p tuyen

cho vat: F, = ma,

Mdmen ciia luc F, dd'i vdi true

quay O : M - F,r = majr

=i> M = I wr jY

- Mdmen tac dung len mdi chat

dilm dupe xac dinh M, = I m^r, 1 Y

- Vl cac cha't dilm ciia vat rin cd

cung mdt gia tdc gdc nen mdmen

tac dung len vat rin dupc xac dinh :

GV neu cac cau hdi gpi y:

- Xet trudng hop don gian nha't la vat

rin gdm mdt qua cau nhd khd'i lupng m

gin vao mdt dau thanh rat nhe, dai /• Vat chi chuyin ddng quay tren mat phing nhin nim ngang xung quanh mdt

true thing diing di qua dau O ciia thanh

Khi dd bilu thiic lien he giira mdmen lire va gia tdc gdc dupe viet nhu the nao ?

- Luc tac dung theo phuang nao thi gay

gia tdc tie'p tuye'n a, cho vat ?

- Mdmen ciia luc F, dd'i vdi true quay

O dupc xac dinh nhu the nao ?

- Gia tdc tie'p tuye'n a, cd lien he vdi

gia tdc gdc Y r^hu the nao ? Bilu thiic

bilu diln mdi lien he giiia gia tdc gdc ciia vat rin va mdmen luc dupc vilt nhu the nao ?

- Ne'u vat rin gom nhilu chat dilm khdi

lucmg Wp m, a each true quay nhirng khoang each i\, /j, khac nhau thi

mdmen tac dung len mdi chat diem dupc vilt nhu the nao ? Mdmen tic dung len vat rin dupc xac dinh nhu the nao ?

Hoat d g n g cua hgc sinh

Hoat d o n g 3

Xay dung khai niem mdmen [

quan tinh, vie't phuong trinh ;

ddng luc hgc ciia vat ran quay ;

quanh mot true cd djnh

HS thao luan chung toan lap va j

dua ra du doan •

- Dai lupng ^ ^ , 7 - , dac trung ;

/ '•

cho miic quan tinh cua vat quay |

HS dua ra cac du doan :

Du dodn I : Dai lupng ^ m,r, phu |

thudc vao mdmen luc tie dung ;

len vat rin va gia tdc gdc ma nd i

phu thudc vao khd'i lupng ciia vat •

rin va su phan bd khdi lupng ciia •

vat rin i

HS thao luan chung toan Idp d l •

thiet ke phuang an thi nghiem

- Can phai cd mdt vat rin, tac ;

dung vao vat rin va do mdmen luc ;

dd, do gia tdc gdc ciia vat rin •

Trg giiip cua giao vien

GV neu cau hdi vl van de cin nghien ciiu:

- Dai lupng ^ w ^ r , trong bilu thiic

/ lien he giira mdmen ciia vat rin vdi gia tdc gdc dac trung cho tinh chat gi ciia vat rin ? Dai lupng dd phu thudc vao nhiing yeu td nao ?

GV neu cac cau hdi gpi y:

- T i r b i l u thiic lien he giira mdmen ciia vat rin vdi gia tdc gdc, vdi ciing mdmen tie dung, vat rin nao cd dai lupng Z ' " , ' ' , Idn thi gia tdc gdc cd gia tri nhu the nao ?,Cd d l dang thay doi van tdc gdc cua vat rin hay khdng ?

GV yeu cau HS thie't ke phuong an thi nghiem d l kilm tra cac du doan tren

GV gidi thieu bd thi nghiem va gpi y

Hoat d g n g cua hgc s i n h Trg giiip cua giao vi§n

- Tac dung luc vao vat ran bing

cac qua gia trpng, luc tac dung vao

vat rin bing luc cang T

- Mdmen luc tac dung vao vat rin:

M = T.R Can phai xac dinh dp Idn

luc T va ban kinh R

Luc T = m^ig - (3|), vdi m,, a, la

khdi lupng va gia tdc ciia qua gia

trpng

- Gia tdc ciia qua gia trpng dupe

2sx xac dinh: a^ = " V '

tx

Vay mdmen luc tac dung vao dTa trdn cd thi

xac dinh :

M=T.R=m\(g-a\)R

=m,(8-^-)R

- Gia tdc gdc cua vat dupc xdc

dinh thdng qua gia tdc tie'p

tuye'n, mat khac gia tdc tie'p

- Chiing ta cd bd thi nghiem: gom cac vat rin la nhiing dTa trdn (1, 2, 3) cd the quay quanh true di qua tam dTa Cac dia trdn gidng nhu cac rdng rpc Tac dung lire vao vat rin bing each nao ?

- Xac dinh mdmen luc tac dung vao vat rin nhu the nao ?

- Tren bd thi nghiem cd bd tri 2 cong quang dien va ddng hd do thdi gian, cd the xac dinh dupe gia tdc ciia qua gia trpng dupc khdng ?

- Gia tdc gdc ciia vat rin dupe xac dinh nhu the nao ?

- Gia tdc gdc ed quan he vdi gia tdc tie'p tuye'n nhu the nao ?

Hoat dgng cua hoc sinh

tuye'n chinh bing gia tdc cua gia

trong Vl vay Y = —^ = — •

R R,t,'

- Tien hanh thi nghiem vdi luc

tac dung la T,, xac dinh dai

lupng y^mjrj tuong irng Sau dd

tiln hanh thi nghiem vdi luc tac

dung 7^2, xac dinh dai lupng

^ W , A ; tuang ling Tir dd riit ra

ke't luan

HS chii y quan sat, ghi sd lieu, xir

li sd lieu va riit ra ke't luan

Ke't ludn : Vdi mdt vat rin cd true

quay nhit dinh, thay doi mdmen

luc tac dung vao vat rin thi gia tdc

gdc thay doi nhung ^/W/A", ludn

la mdt hing sd Vay dir doan 1 la

khdng chinh xac

- Can phai tien hanh thi nghiem

vdi hai dTa trdn cd cung chat cau

tao, cung khd'i luang nhung ban

kinh khac nhau (su phan bd khdi

lupng khac nhau) Xac dinh dai

lupng Z»i,r,^ (viec xac dinh dai

Trg giiip ciia giao vien

- Can phai tien hanh thi nghiem nhu the nao dl kilm tra du doan 1

GV tien hanh thi nghiem d l kilm tra du doan thii nha't ciia HS

GV neu cau hdi vl thi nghiem can phai tiln hanh dl kiem tra du doan 2

- De kilm tra du doan 2 can phai tien

hanh thi nghiem nhu the nao ? Biet ring eac dTa trdn cd khd'i lupng va ban kinh

lan lupt nhu sau : W] = 800g, R^ = 5cm; W2 = 800g, R2 = 2,5cm; m^ = 400g, /?3 = 5cm

Hoat dgng cua hgc sinh Trg giiip cua giao vien

lupng ^m^ri gidng nhu thi

nghiem vira tien hanh d ben

tren) Tir dd riit, HS ra ket luan

- Can phai tien hanh thi nghiem

vdi hai dTa trdn cd cung ban kinh

nhung khdi lupng khac nhau Xac

dinh dai lupng ^ w / , Tit dd,

HS riit ra kit luan

HS chii y quan sat, ghi sd lieu, xir

li sd lieu va riit ra kei luan

Kei ludn : Dai lupng ^ OT,r, khdng

chi phu thudc vao khdi lupng eiia

vat rin ma cdn phu thudc vao sir

phan bd khdi lupng cua vat rin

HS tiep thu, ghi nhd

GV tien hanh thi nghiem

GV thdng bao:

- Mdmen quan tinh / ddi vdi mdt true la dai luong dac trung cho miic quan tinh cua vat rin trong chuyin ddng quay quanh true ay

i

- Dp Idn ciia mdmen quan tinh cua vat

rin khdng chi phu thudc vao khd'i lupng ciia vat rin ma cdn phu thudc vao su phan bd khd'i lupng ciia vat rin

- vay ta cd thi vie't: M - l.y, phuang

trinh nay gpi la phuang trinh ddng luc hpc ciia vat rin quay quanh mdt true

Hoat dgng ciia hgc sinh

Hoat dong 4

Van dung phuong trinh co ban ;

ciia chuyen ddng quay ciia vat :

rin de lam bai tap

HS suy nghT ca nhan, sau dd thao ;

luan nhdm va dai dien nhdm len ;

bao cao kit qua ;

Ap dung dinh luat II Niu-ton cho ;

chuyin ddng tinh tiln cua thiing ;

nude, ta cd : ;

mg-T = ma (1)

Ap dung phuang trinh ddng luc •

hpc cho chuyin ddng quay cua vat ;

Cling cd bai hgc va dinh hudng :

nhiem vu hoc tap tie'p theo

Trg giiip cua giao vien

Day la phuang trinh co ban ciia chuyin ddng quay ciia vat rin

GV yeu ciu HS lam viec vdi phieu hpc ••

tap dl lam bai tap 1

GV neu cac cau hdi gpi y:

- Viet phuang trinh dinh luat 11 cho thiing nude

- Viet phuang trinh ddng lire hpc cho vat rin la hlnh tru cd true quay

- Mdmen quan tinh dupc xac dinh nhu the nao ?

- Gia tdc gdc dupc xac dinh thdng qua gia tdc tie'p tuye'n nhu the nao ?

- GV yeu eau HS lam viec vdi bang 2.1 SGK dl tim sir tuong tu giira hai phuang

Hoat d g n g ciia hgc s i n h

HS lam viec chung toan Idp

Trg giiip cua giao v i e n trinh ddng luc hpc cua chuyin ddng quay va chuyin ddng tinh tien

- GV yeu eau HS lam bai tap cdn lai trong phieu hpc tap

- HS vl nha lam cac bai tap cdn lai trong SGK

- HS vl nha dn lai cac kie'n thiic vl ddng lupng va dinh luat bao toan ddng lupng d vat li Idp 10 THPT

PHIEU HOC TAP

Cau 1 Mdt thimg nude dupe tha xudng gilng nhd

mdt spi day dai quan quanh mdt hinh tru cd

ban kinh R va mdmen quan tinh / Khd'i

lupng cua day khdng dang ke Hinh tru coi

nhu quay tu do khdng ma sat quanh mdt true

cd dinh Khd'i lupng cua thiing nude la m

Tinh gia tdc cua thiing nude

Cau 2 Mdt mdmen lire khdng ddi tac dung vao mdt vat co iiuv quay cd dinh

Trong nhirng dai lupng dudi day, dai lupng nao khdng phai la hing so ?

A Mdmen quan tinh B Gia tdc gdc

C Khd'i lupng D Tdc dp gdc

Cau 3 Hai chat dilm cd khd'i lupng 1 Z:^ va 2 kg duac gin d hai dau cua mdt

thanh nhe cd chilu dai Im Mdmen quan tinh cua he, dd'i vdi true quay di

qua trung dilm cua thanh va vudng gdc vdi thanh, cd gia tri

A 1,5 kg.m

C 0,5 kg.m^

B 0,75 kg.m^

D 1,75 kg.m^

Cau 4 Mdt vat hinh cau dac khd'i lupng m = 0,5kg,

ban kinh R = 0,2m Mdmen quan tinh ciia nd

dd'i vdi true quay di qua tam la

A 0,02 kg.m^

B 0,04 kg.m^

C 0,06 kg.m^

D 0,08 kg.m^

Cau 5 Ke't luan nao sau day sai khi ndi vl mdmen quan tinh cua vat rin ?

Mdmen quan tinh cua vat rin phu thudc vao

A khd'i lupng ciia vat

B gia tdc gdc cua vat

C hlnh dang va kich thudc cua vat

D vi tri cua true quay

- Hiiu dupe khai niem mdmen ddng lupng

- Nim dupc dinh luat bao toan mdmen ddng lupng, dilu kien d l mdmen ddng lucftig cua vat rin chuyin ddng quay dupe bao toan

- Hiiu dupc thi nghiem kilm nghiem mdt each dinh tinh dinh luat bao toan mdmen ddng lupng

III - THlfiT Kfi' H O A T D O N G DAY - H O C

Hoat d g n g cxla hgc s i n h Trg giiip cua giao vien

Hoat dgng 1

Kiem tra, chuan bj dieu kien

xuait phat Dat vain de

HS suy nghT ca nhan tim cau tra Idi

Dang khac ciia phuang trinh dinh

luat II Niu-ton : F = -^ trong dd

- Viet dang khac ciia phuong trinh dinh luat II Niu-ton

Hoat d g n g cua hgc sinh

APla dp bie'n thien ddng lupng

trong khoang thdi gian At

HS nhan thirc dupe va'n dl ciia bai

hpc

Hoat dgng 2

Xay dung khai niem mdmen

ddnglugng

HS thao luan chung toan Idp dl tim

dang khac cua phuang trinh ddng

lire hpc ciia vat rin chuyin ddng

Trg giiip cua giao vien

Dgt van de : Khi viet phuang trinh dinh

luat II Niu-ton dang I ta cd thi tim dupc

su tuong tu giira phuang trinh dinh luat

II Niu-ton vdi phuong trinh ddng lire hpc cua vat rin chuyin ddng quay quanh mdt true Cd sir tuang tu giira phuang trinh ddng luc hpc ciia vat rin chuyin ddng quay quanh mdt true vdi phuang trinh dinh luat II Niu-ton dang khac khdng? Bai hpc ngay hdm nay se nghien ciiu dilu dd

GV neu cau hdi dl HS tim su tuong tu giira phuong trinh ddng luc hpc cua vat rin chuyen ddng quay vdi phuang trinh dinh luat II Niu-ton dang khac

- Mud'n tim su tuong tu giiia phuong trinh ddng luc hpc cua vat rin chuyin ddng quay vdi phuong trinh dinh luat II Niu-ton dang khac ta phai tim dupe dang khac cua phupng trinh ddng luc hpc cua vat rin chuyin ddng quay Dang khac ciia phuong trinh ddng lire hpc cua vat rin chuyin ddng quay cd dang nhu the nao ? Sir tuong tu ciia nd vdi phuong trinh dinh luat II Niu-ton dang khac la gi ?

GV neu cac cau hdi gpi y:

- Viet bilu thiic dinh nghia gia tdc gdc

- Ne'u mdmen quan tinh / khdng doi thi

cd thi viei phuong trinh ddng luc hpc cua vat ran chuyin ddng quay nhu the nao ?

Ne'u tong cac mdmen lire tac dung

len mdt vat rin (hay he vat) dd'i vdi

mdt true quay bing khdng thi tong

mdmen ddng lupng cua vat (hay he

vat) ddi vdi true dd dupc bao toan

Trg giiip cua giao vi§n

- Neu su tuang tu cua phuang trinh ddng luc hpc cua vat rin chuyin ddng quay vira tim dupc vdi phuang trinh dang khac ciia dinh luat II Niu-ton

trong chuyin ddng tinh tien Vi the, ta

gpi L - lco la mdmen ddng lupng cua

vat rin dd'i vdi true quay

- Don vi ciia mdmen ddng lupng la

GV neu cac cau hdi gpi y

- Ne'u mdmen ddng lupng L dupc bao

toan thi ddng bie'n thien cua mdmen ddng lupng bing bao nhieu ?

- Tir phuang trinh M - — tim dilu

dt

kien dl mdmen ddng lupng cua vat hoac

he vat dupc bao toan

Hoat d6ng cua hgc sinh

Vi mdmen ddng lupng dupc bao

toan n e n : I\COi = I2CO2

HS thao luan chung toan Idp

- Can phai cd mdt vat rin, thay doi

tdc dp gdc hoac mdmen quan tinh

cua vat, do / va co tuong irng Sau

dd tinh tich : lco Ne'u mdmen

ddng lupng cua vat dupe bao toan

thi tich lo) = hing sd

HS chu y quan sat

HS thao luan chung toan Idp

- Can phai truyin cho he vat gdm

ngudi va dia quay mdt tdc dp gdc,

thay doi mdmen quan tinh ciia he

bing each dang hai tay cam ta

hoac CO hai tay cam ta lai Quan

sat su thay doi tdc dp gdc ciia he vat

HS chii y quan sat va rut ra kei

luan

- He vat da dupe truyen mdt tdc dp

gdc, khi dang hai tay cam ta ra thi

mdmen quan tinh tang, tdc dp gdc

Trg giiip cua giao vien

GV neu cau hdi d l HS thiei ke phuang

an thi nghiem kilm nghiem lai dinh luat bao toan mdmen ddng lupng

- Thiei ke mdt phuang an thi nghiem dl kilm nghiem lai dinh luat bao toan mdmen ddng lupng

GV gidi thieu bd thi nghiem vdi g h i Giucdpxky

- Ghe Giucdpxky la mdt dTa kim loai cd thi quay quanh mdt true cd phuang thing diing tren mdt de nam ngang

GV neu cau hdi cho HS tien hanh thi nghiem vdi ghe Giucdpxky:

- Cho mdt ban cam hai qua ta tren hai tay va diing len ghe, can phai tien hanh thi nghiem nhu the nao dl kilm nghiem mdt each dinh tinh dinh luat bao toan mdmen ddng lupng?

GV cho 2 HS tien hanh thi nghiem

Hoat dgng cua hgc sinh Trg giiip cua giao vien

ciia he vat giam Ngupc lai, khi co

hai tay cam ta lai, mdmen quan

tinh cua vat giam, tdc dp gdc cua

he vat tang

Vay, mdt each dinh tinh, chiing ta da kilm nghiem dupc dinh luat bao toan ddng lupng la diing

Hoat dgng 4

Cling cd bai hgc va dinh hudng

nhiem vu hgc tap tie'p theo

HS lam viec ca nhan, sau dd thao

luan chung toan Idp

- GV yeu ciu HS lam bai tap trong phieu hpc tap

- HS vl nha lam cac bai tap cdn lai trong SGK

- On lai eac kie'n thiic vl ddng nang va

dd bie'n thien ddng nang da hpc d Vat 11

10 THPT

PHIEU HOC TAP

Cau 1 Mdt vat cd mdmen quan tinh 0,12kg.m^ quay diu 10 vdng trong \,%s

Mdmen ddng lupng ciia vat cd dp Idn bing

A 4 kg.m^ls B 8 kg.m^ls

C 13 kg.m^/s D 25 kg.m^/s

Cau 2 Hai dia trdn cd mdmen quan tinh /, va I2

dang quay ddng true va eiing chilu vdi

tdc dp gdc ffl] va CO2 nhu hinh ben Ma

sat d true quay nhd khdng dang kl Sau

dd cho hai dTa dinh vao nhau, he hai dTa

quay vdi tdc dp gdc co c6 dp Idn dupe

xac dinh bang cdng thiic

Cau 3 Mdt vat rin cd mdmen quan tinh Ikg.m"^ quay diu 10 vdng trong 2s

Mdmen ddng lupng ciia vat rin cd dp Idn bing

A 3,l4lkg.m^/s B 3l,4lkg.m'^/s

C.3l4,lkg.m'^/s D.3l4lkg.m^/s

BAI4

DONG NANG CUA VAT RAN

QUAY QUANH M O T TRUC c 6 BJNH

I - MUC TifeU

1 Ve kien thiic

- Biei dupe khi mdt vat rin quay (quanh mdt true) thi vat cd ddng nang

- Biei so sanh dai lupng tuong ling trong bilu thiic eiia ddng nang quay va ddng nang trong chuyin ddng tinh tien

- Hiiu va ap dung dupe dinh luat bie'n thien ddng nang cua vat rin trong chuyin ddng quay

- Giai cae bai toan don gian ve ddng nang ciia vat rin trong chuyin ddng quay

- van dung kie'n thiie dl giai thich mdt sd hien tupng trong thue te, biet cac ling dung ciia ddng nang quay trong kT thuat

2 Ve kl nang

- Ren luyen kT nang Idgic toan hpc dl tim bilu thitc ddng nang cua vat rin trong chuyin ddng quay

- Ren luyen kT nang giai thich cae hien tupng vat li vl ddng nang cua vat rin

- Ren luyen kT nang giai cac bai toan vl ddng nang va dp bie'n thien ddng nang ciia vat rin quay

Ill - THifeT K£' HOAT D O N G DAY - HOC

Hoat d g n g ciia hgc s i n h

Hoat dgng 1

Kiem tra, chuan bi dieu kien ;

xuat phat Dat van de

HS suy nghT ca nhan, sau dd thao ;

luan chung toan Idp :

- Trudng hpp may mai quay nhanh ;

thi dTa may se cd nang lupng Idn :

hon vi cd kha nang sinh cdng lam |

mai mdn cae vat va gay ra su toa •

nhiet •

Ca nhan nhan thirc dupe van d l |

ciia bai hpc •

Hoat dgng 2

Xay dung bieu thiic tinh dgng |

nang cua vat rdn quay quanh ;

mgt true cd dinh

HS suy nghT ca nhan i

T r g giiip cua giao v i e n

GV neu cau hdi kiem tra kie'n thiic cu:

- So sanh nang lupng ciia dTa may mai trong hai trudng hpp : may mai quay nhanh va may mai quay cham

Dgt van de : Nang lupng cua dTa may

mai khi quay gpi la ddng nang cua vat rin (dTa mai) quay quanh true cd dinh Bilu thiic tinh ddng nang cua vat rin quay quanh true cd dinh dupc xac dinh nhu the nao ? Bai hpc ngay hdm nay giiip chiing ta xay dung bilu thiic dd

GV yeu cau HS tim bieu thu:c tinh ddng nang ciia vat rin quay quanh mdt true

Hoat dgng cua hgc sinh

Cac chai dilm chuyin ddng quay

vdi ciing tdc dd gdc, ddng nang

cua mdt chat dilm dupe xac dinh :

-w,v, =-m,{cor^)

Ddng nang cua vat rin bing tong

ddng nang cua cac chat dilm cau

thanh vat:

^^ V / \2 1 , 2

Hoat dgng 3

Xay dung bieu thurc ciia djnh If

bien thien dgng nang ciia vat ran

quay quanh mgt true cd djnh

Trg giiip cua giao vien

GV neu cac cau hdi gpi y:

- Coi vat rin gdm nhilu chat dilm, mdi chat dilm cd khd'i lupng m; va each true quay mdt khoang /•; Van tdc gdc ciia cac chat dilm nay cd dac dilm gi ?

- Ddng nang ciia mdi chat dilm dupe xac dinh nhu the nao ?

- Ddng nang cua vat rin dupe xac djnh nhu the nao ?

GV neu cau hdi vl van dl can nghien ciru:

- Khi vat rin quay quanh mdt true cd

dinh chiu tac dung cua ngoai luc F

khdng doi va ludn tiep tuyen vdi quy dao dilm dat thi ddng nang cua vat rin thay doi Dp bie'n thien ddng nang ciia vat rin dd cd quan he nhu the nao vdi

cdng cua ngoai luc F ? Bilu thiic toan

hpc nao bilu thi mdi quan he dd ?

GV neu cac cau hdi gpi y:

- Yeu eau HS lam viec vdi phieu hpc tap dl tra Idi cau 1

- Cdng cua luc F dupe xac dinh nhu the

nao ?

- Cdng ciia lire F cd quan he nhu the

nao vdi mdmen ciia luc F ?

- Viei bilu thii'c lien he giiia tdc dp gdc, gia tdc gdc va dp bie'n thien toa dp gdc

Hoat d g n g cua hgc s i n h

HS tilp thu, ghi nhd

Hoat dgng 4

Ap dung cdng thurc tinh dgng

nang ciia vat ran quay quanh

mot true cd dinh de lam bai tap

HS lam viec ca nhan vdi phieu

hpc tap

Ddng nang liic diu cua vat la :

f^d(dau)=^/l^'=202,5J

Vi mdmen lire tac dung vao van

ddng vien bing 0 nen theo dinh

luat bao toan mdmen ddng lupng,

Cling cd bai hgc va dinh hudng

nhiem vu hgc tap tiep theo

T r g g i u p cua giao v i e n

GV thdng bao:

- Bilu thiic A = -Io)j lo}? =AW la

2 ^ 2 bilu thiie ciia dinh li bie'n thien ddng nang

- Dinh li bie'n thien dgng ndng : Dd bie'n

thien ddng nang cua mdt vat bing tdng cdng cua cae ngoai lire tac dung vao vat

GV yeu cau HS lam viec vdi phieu hpc tap dl lam bai tap 2

GV neu cac cau hdi gpi y:

- Xac dinh ddng nang bing cdng thirc nao ? Ddng nang ban diu dupc xac dinh nhu the nao ?

- Mud'n xac dinh dupc ddng nang liic cud'i can phai xac dinh dupc dai lupng nao ?

- Theo dinh luat bao toan mdmen ddng lupng, ta cd thi tinh dupc tdc dp gdc liic cud'i nhu the nao ?

GV yeu cau hpc tim su tuang tu giira bilu thiic ddng nang ciia vat rin quay

Hoat ddng cua hgc si^h

HS lam viec ca nhan, sau dd thao

luan chung toan Idp

Trg giiip cua giao vien

quagh mgt true cd dinh vdi bilu thu'c ddng nang cua vat chuyin ddng tinh tig'n va lam cae bai tap cdn lai trong phieU hpc tap

- Vl nha lam cac bai tap trong SGK

- On cac kie'n thiic, eac cdng thiic va ,phuang trinh ddng lire hpc cua chuyin ddng quay

- On lai phuang phap ddng lire hpc da hoc d Idp 10 THPT

PHil^U HOC JAP

Cau 1 Mdt vat rin chiu iac dung cua mdt luc F cd dp

Idn khdng doi va ludn ludn tiep tuye'n vdi quy

dao chuyin ddng cita dilm dat Trong qua

trinh chiu F tac dung, vat rin quay dupc mdt

gdc g) thi tdc dp gdc thay doi tir coy de'n

co2.T{nh cdng cua ngoai luc F theo tdc dp gdc

va mdmen quan tinh cua vat rin

Cau 2 Mdt van ddng vien trupt bang quay quanh mdt true thing dung vdi tdc dp

gdc 15 radls vdi hai tay dang ra, mdmen quan tinh ciia ngudi liic nay ddi vdi true quay la 1,8 kg.m Sau dd ngudi nay ddt ngpt thu tay lai dpc theo

than ngudi, trdng khoang thdi gian nhd tdi miic cd thi bd qua anh hudng cua ma sat vdi mat bang Mdmen quan tinh cua ngudi liic dd giam di ba lin so vdi liic dau Tinh ddng nang cua ngudi dd liic dau va luc cuoi

Cau 3 Hai vat rin cd cung mdmen quan tinh va cd ddng nang lien he vdi

nhau theo bieu thiic W^ ^2W^ Kei luan nao sau day diing khi ndi vl

tdc dp gdc ciia hai vat rin ?

- Du kie'n cac sai lam (vl kie'n thiic va phuang phap) ma HS cd thi mic phai khi

giai bai tap

- Chuin bi phieu hpc tap cho HS

Hpc sinh

- On cac kie'n thiic, cae cdng thirc va phuong trinh ddng lire hpc cua chuyen ddng

quay dl cd thi giai dupc cac bai tap vi du dudi sur gpi y cua GV

- On lai phuang phap ddng lire hpc d Idp 10

III - THlfiT Kfi' HOAT D 6 N G DAY - HOC

Hoat dgng cua hgc sinh

Hoat dgng 1

Kiem tra, chuan bj dieu kien

xua't phat

Trg giiip cua giao vien

GV neu cau hdi kilm tra kie'n thiic cu:

- Viet cdng thiic dinh nghTa gia tdc gdc ciia vat rin chuyen ddng quay ?

Hoat ddng cua hgc sinh Trg giiip cua giao vien

HS suy nghT ca nhan tim cau tra

Idi

- Viei phuang trinh ddng lire hpc ciia vat rin quay quanh mdt true cd dinh ?

- Viet cdng cdng thirc tdc dp gdc va phuang trinh chuyin ddng cua vat rin quay quanh mdt true cd dinh ?

Hoat dgng 2

Lam bai t$p 1 de dn tap lai cac

kien thurc da hgc ve chuyen dgng

quay ciia vat ran quanh mgt true

HS lam viec ca nhan sau dd thao

luan chung toan Idp

a) Gia tdc gdc cua banh xe dupc

b) Mdmen quan tinh cua banh xe

dd'i vdi true quay

Tong mdmen tac dung vao banh xe

d giai doan quay nhanh dan deu:

GV neu cac cau hdi gpi y:

- Ap dung cdng thiic nao d l tinh gia tdc gdc ?

- Trong giai doan dau van tdc gdc bie'n thien nhu the nao ?

- Khoang thdi gian xay ra bie'n thien dd bing bao nhiSu ?

- Ap dung cdng thiic nao dl tinh mdmen quan tinh cua vat rin dd'i vdi true quay ?

- Trong phuang trinh ddng luc hpc ciia vat rin chuyin ddng quay quanh mdt true, dai lupng nao da biei, dai lupng nao chua biet ?

- Dl biet dupc gia tdc gdc trong phuang trinh, ta can phai viei phuang trinh ddng lire hpc cua vat rin trong giai doan nao ?

- Trong giai doan dd, mdmen dupc xac dinh nhu the nao ? Cd miy mdmen lire tac dung vao vat trong giai doan dau?

- Mdmen tong hpp dupe xac dinh nhu the nao ?

_ ^ ^

Hoat dgng cua hgc sinh

c) Ddng nang quay ciia banh xe d j

diu giai doan quay cham dan diu:

IV =-Ico? =-.20.15^ =\\25J \

2 2 ;

Hoat dgng 3

Lam bai tap 2 de bie't each ap ;

dung phuong trinh ddng luc hgc \

cua vat ran quay

HS lam viec ca nhan sau dd thao |

luan chung toan Idp •

Trg giiip cua giao vi§n

- Ap dung cdng thu'c nao dl tinh ddng nang quay ciia vat rin ?

GV yeu cau HS lam viec vdi phieu hpc tap dl lam bai tap 2

GV neu cac cau hdi gpi y:

- Mdmen quan tinh cua dTa trdn ddng chat dupc xac dinh nhu the nao ?

- Dl tinh dupc mdmen ham, ta can phai tinh them dai lupng nao niia ?

Hoat ddng cua hgc sinh Trg giiip cua giao vien

Hoat dgng 4

Tim hieu khai niem he quy chieu

va chuyen ddng tjnh tien

HS lam viec ca nhan sau dd thao

luan chung toan Idp

a) Tinh gia tdc gdc cua rdng rpc

1 2 2fi)

Tir cdng thuc cp^ — yt ^ / —

-Thay sd : y =•

2 2.4n

- Gia tdc cua vat A va B lien he nhu the

nao vdi gia tdc tiep tuye'n cua rdng rpc ?

- Viet cdng thirc lien he giira gia tdc tie'p tuyln vdi gia tdc gdc ciia rdng rpc ?

- Phan tich luc tie dung vao cac vat va vao rdng rpc ?

- Viet phuang trinh chuyin ddng cho vat A ?

- Luc cang T^ va Tg cd dd Idn bing

nhau khdng ? Tai sao ?

- Tong hpp mdmen luc tie dung vao rdng rpc bing bao nhieu ? Cd bing 0

Hoat dgng cua hgc sinh Trg giiip cua giao v i e n

{TA-TB)-I^^TB=T,-1^

Thay sd:

To = 9 , 1 7 - 0 , 0 5 6,28

0,1 = 6,03Ậ

d) Vi Tg - 6,03N > ma, suy ra giiia

vat B va ban ed ma sat, dp Idn cua

luc ma sat dupc tinh nhu sau :

- So sanh đ Idn cua luc cang Tg vdi

tich ma ? Cd ket luan gi vl dilu nay ?

- Luc ma sat dupe xac dinh nhu the nao ?

- Viet phuang trinh dinh luat II Niu tan

cho vat B ?

M

mg

5,4 1.9,8 = 0,55

Hoat dgng 5

Cung cd' bai hgc va dinh hudng

nhiem vu hgc tap tiep theo

GV hudng din HS tim hiiu sir tuong tu giQa cac dai lupng gdc dac trung chuyin đng quay va dai lupng dai dac trung cho chuyin đng thing d phin tdm tit chuang Ị

- On lai vl dao ham, each tinh dao ham,

y nghTa vat li cua dao ham

PHIEL HOC TAP

Cau 1 Mdt banh xe dap chiu tic dung ciia mdt mdmen luc M, khdng doi la

20/V.m Trong 10^ dau, tdc dp gdc cua banh xe tang deu tir 0 dén \5radts

Sau đ mdmen M, ngtoig tac dung, banh xe quay cham dan diu va dimg

hin lai sau 30i' Cho biet mdmen ciia luc ma sat cd gia tri khdng ddi trong sudt thdi gian banh xe quay va bang 0,25JV/,

a) Tinh gia tdc gdc cua banh xe trong cac giai doan quay nhanh din diu

va quay cham dan diu

b) Tinh mdmen quan tinh cua banh xe dd'i vdi true

c) Tinh ddng nang cua banh xe d dau giai doan quay cham din d6u

Cau 2 Mot dia trdn ddng chat khd'i lupng m = I kg, ban kinh R - 20cm dang quay

diu quanh mdt true vudng gdc vdi mat phang dTa vdi tdc dp gdc

COQ =\OradlS Tac dung len dia mdt mdmen ham DTa quay cham dan diu va dumg han sau khi da quay dupe mdt gdc \Orad

a) Tinh mdmen ham dd

b) Tinh thdi gian tir liic chiu tac dung ciia mdmen ham de'n khi dTa dimg hin

Cau 3 Hai vat A va B cd ciing khdi

lupng m= \kg, dupe lien kei vdi

nhau bing mdt spi day nhe, •"•'' 'i i • •[

khdng gian, vit qua rdng rpc cd

ban kinh 10cm va mdmen quan

tinh / = 0,050kg.m^ Biet day

khdng trupt tren rdng rpc nhung

khdng biei giiia vat B va ban cd

ma sat hay khdng

Liic dau eac vat dupe giii diing yen, sau dd he dupc tha ra Ngudi ta thay

sau 2s, rdng rpc quay quanh true cua nd dupc 2 vdng va gia tdc ciia cac khd'i A, B khdng doi Cho g = 9,Sm/s^ Coi ma sat d true cua rdng rpc

khdng dang kl

a) Tinh gia tdc ciia rdng rpc

b) Tinh gia tdc ciia hai vat

c) Tinh luc cang cua day d hai ben cua rdng rpc

d) Cd ma sat giiia vat B va mat ban hay khdng Neu cd, hay tinh he sd ma sat

B

IZZ

B Al KlfiM TRA CHUONG I

I - MUC TifiU

- Ciing cd, khic sau kie'n thiic d chuang I

- Ren luyen diic tinh trung thue, can cii, cin than, chinh xac, khoa hpc Phat huy kha nang lam viec ddc lap d I^S

II - CHUXN BI

Giao viSn

- Dl bai kilm tra theo miu

Hpc sinh

- Kiln thiic toan chuang I

Ill - THifi'T Kfi' PHUONG A N DAY HOC

Hoat dgng cua hgc sinh

Trd giup cua giao vien

GV kilm tra sT so HS va neu yeu ciu

vl ki luat dd'i vdi gid kiem tra

GV phat bai kilm tra tdi tirng HS t^uaa I( HS lam bai, dam bao tinh ediig bang, trung thuc trong khi lam bai

GV thu bai va nhan xet vl ki luat gid hpc

NOI DUNG KIEM TRA

I - BAI TAP TRAC NGHIEM

1 Khoanh tron trudc dap an ma em lua chgn (Chu y : mdi cdu chi duac lua chgn mgt ddp dn)

Cau 1 Kei luan nao sau day diing khi ndi vl chuyin ddng cua mdt dilm tren

vat rin quay quanh mdt true cd dinh ?

Khi vat rin quay

A eac dilm khac nhau tren vat rin quay vdi tdc dp gdc khac nhau trong cimg mdt khoang thdi gian

B mdi dilm tren v&t rin vach mdt dudng trdn nim trong mat phing vudng gdc vdi true quay

C cac dilm khac nhau tren vat rin quay dupc cac gdc khac nhau trong eiing mdt khoang thdi gian

D mpi diem tren vat rin cd ciing mdt tdc dp dai

Cau 2 Mdt dTa CD quay diu vdi tdc dp quay 450 vdng/ phiit trong mdt 6 dpc

cua may vi tinh Tdc dp gdc cua dTa CD dd tinh theo rad/s la

A 410radls B 41 radls

C 4,lradls D 0,41radls

Cau 3 Mdt vat bit dau quay diu quanh mdt true cd dinh, sau 2s dat dupc tdc

dp gdc lOrad/s Gia tdc trung binh cua vat trong thdi gian dd la

A 5radls^ B lOrad/s'^

C.\5radls^ D.25radls^ Cau 4 Mdt diem tren vat rin each true quay mdt doan R Khi vat rin quay

diu quanh true vdi van tdc gdc co thi tdc dp dai cua dilm dd la

A v = —• B v = —•

R : CO

C. V = CO.R\ D V = CO.R