NGHIEN CUU & UNG DUNG III BO THI NGHIEM MO TA CHUYEN DONG QUAY VA ROl TU DO CUA MOT VAT ThS Trdn Thj Thanh Thu Trudng DH DSng Tlidp SUMMARY Nowadays, using the self creation experiments in teaching in[.]
N G H I E N CUU & UNG DUNG III BO THI NGHIEM MO TA CHUYEN DONG QUAY VA ROl TU DO CUA MOT VAT ThS Trdn Thj Thanh Thu Trudng DH DSng Tlidp SUMMARY Nowadays, using the self-creation experiments in teaching in high schools and universities is becoming popular It not only helps students understanding and mastering their knowledge deeply to explain or conduct experiments by themselves but also creates comfortable learning atmosphere in the classroom In this paper, we present the experiment system describing the rotational andfree falling object motion Tir khda.' Self-creation experiments; rotational object motion;freefalling object motion Ng^ nh^n bii: 19/5/2014, duyft ddng: 23/5/2014 Hi^n nay, vi$e sd dyng thi nghipm ty tgo (TNTT) dgy hpe d cde trudng THPT vd cdc trudng dai hpc ngdy cdng trd ngn phd biln Nd khdng nhttng giup cho ngudi hpe dao sdu kien thde, nim vQng npi dung qud trinh vdn dyng kiln thirc dg gidi thich hoac ehl tgo dyng ey thi nghifm md cdn gdy hdng thd, tgo bdu khdng kh( hpc tgp thodi mdi Idp hpe Sau ddy tdi xin gidi thi^u mdt bO TNTT vda md td chuyin ddng quay vira md td chuygn ddng roi ty cua mdt vdt l.Thf nghiem Myc dich cda tlti nghiem: Khdo sdt gia tdc cua vgt chuyin ddng quay, so sdnh vdi gia tdc cua v§t roi ty Dung cu till nghiem: Hai tim bdn gd (1) va (2) gidng (ddi 120 em, ngang 20 em, ddy 1,5 em) duge gin vdi bing mdt ban ll (3) Mdt hdp (eh|u) nhd ed dudng kinh cm (4) dupe dat cd djnh trgn tdm gd (2) Mdt vign bi dudng kfnh cm (5) Mdt gd nhd dl tgo gde md (6) Tit ca dugc bl trf nhu hinh Tiin hdnh tiif nghiem: Hai tim gS, mpt tim (tdm g6 1) dgt nam ngang, tim cdn Igi (tim gd 2) hgp vdi m?t phdng ngang mdt gde a (gdc a thay ddi dupe) trdn dd ed gin hdn bi vd mdt ch§u nhd Hdn bi vd ch§u d$t cdch 15 cm, ch§u cdch ban ll 102,5 cm (nhu hinh 2), tim g5 ndy cd thl quay dupe 4cm 13J 2.5cm 102,5cm '„ ti • 15cm • Hinh Kgo tdm gd (2) lgn hgp vdi tdm gd (1) theo mdt gde a (hinh 1), sau dd hudng tay de tdm gd (2) roi xudng, sS xdy hai trudng hgp: + Trudng hgp I: tam gd roi xudng mat phang ngang thi hdn bi roi vdo ehau nhd - thi nghipm thdnh edng (hinh 3) Hinh + Trudng hgp 2: tim gd roi xudng m^t phing ngang thi hdn bi khdng roi vdo chgu nhd - Ihi nghi?m that bgi TAP CHi THI^ BI GlAO DyC - s6 106 - 6/2014 31 NGHIEN CCrU & UNG DUNG Qua thi nghiem eho thiy hdn bi cd roi vao a: Id gdc hgp bdi hai tdm g§ chgu hay khdng hodn todn phy thudc vdo gdc a Do Ggi I Id mdmen qudn tinh cua tim g§ Ap dyng dd, dl thi nghigm thdnh cdng, vigc xdc dinh bien dO cdng thiie xdc djnh mdmen qudn tinh cho cua a Id rdt quan trgng ehuyen d^ng quanh mdt tryc cd dinh Gidi thich thinghi$m Taed: I = -ml} * Gidi thich djnh tinh: Ggi; -i- OA la khoang cdch td dilm tya O din chdu trgn tim gd (2) Mdmen quay ^ : + OB Id khoang cdch tiJr dilm tya O din hdn M = rJy = — m g c o s a bi trgn tim gS (2) A B Hinh Khi thd tim g§ (2) roi xudng trung vdi tim gd (Othlvjtri A = A' yi B = B\ Do eh|u gin e6 dinh trgn tim gd tgi A ngn thd tdm gS (2) roi xudng th! vi tri eua chgu nim d A = A M$t khde, vign bi d vi tri B lgi roi vdo chdu d ddng vj tri A' theo phuong thing ddng Dilu dd cho thiy vign bi roi xudng m^t phing ngang chi chju tde dyng cua trpng lyc P = mg cd phuong vudng gde vdi mat phing ngang ndn vi tri cua vien bi sau roi d diing vj yi A' • Gidi thich dinh lugng (xdc dinh gid tri cda gdc a): Gid thilt tim go ehuyen ddng, nd chi chiu tdc dyng cua hai lye: trgng lyc eua tdm go va phdn lye cua ban le Gia tdc gdc: M Y= — = — g c o s a ' I 2L^ Gia tdc ddi: a = yL=—gcosa a^ = a c o s a = — g c o s a D I hdn bi roi vdo chgu thi a phdi thda man dilu kx^xv.a^ >g Thay gid tri eua a^ vdo bdt dSng thdc ta cd: -gcos a > g = > c o s a > =>0g Thay gid tri eua a^ vdo bdt dSng thdc ta cd: -gcos a > g = > c o s a > =>0