PHiN CHUNG CHO CAC THi SINH:
C(ru I. M6t con ldc ld xo dao dQng diau hdq vo'i tdn sd gdc co : 5T rqd/s vd pha ban ddtt ,p = -+ rad. Uoi sau ntlt tho'i
, J ' :. IJ
gian ttgdrt rtltdt ndo tfu6'i ddy (rin!t tir khi cott ldc bdt ddu dao dQng) dQng ndng dao dong bdng th€ ndng dao*dQng
Gi6i: W,= Wa + W. Cos2(rot + rp) = W.sin2(cot + rp)
= art+ I : -tr +k.L.
Thoi gian ngin nh6t ifnh tt l<hi con lac bat dAu dao dQng ld: I =
5n
CAu 2. M6t cott liic ld xo c6 h€ sii dan hii k = 60 N/m treo thdng dt?ng vdo mot gid co dinh. O vi tri cdn bang td xo bi gidn 5 cm. Con ldc dao d6ng diiu hda r,6'i tti€tt do A : 3 cm. Tai vi tri cao nhdt cuq vqt ndng, ld xo tdc dyngvdo gid d6'mot luc c6 d6 l6n ld:
Girii: F: k(Al- A):60.(5 - 3).10-2 = 1,2 N.
Cdu 3, EQrtg ndng cua nt6t t,dt dao d6ng diiu hda bi6n rhi€n tudu hoan t 6'i t,in sii f : 5 Hz. Chu ki dao dong ctra vdt ld: -
^,.,. "-). i. , ,;. a, 'a
Gi6i; Tdn s6 dao d6ng cua vAt chi bdng m6t nua tAn sd bi6n thi6n cua d6ng ndng = fq: 2,5 Hz = T = l/f :0,4 s.
Cliw 4. Con ldc clon c6 chiiu ddi I = 20 cm. Tai thd'i di€m t :0 con ldc dve'c trryin vdn toc l4 cm/s tivi tri cdn bing theo ciri€tr cl.trottg cua truc tqa dQ. L,iy C: 9,8 mis2. Phrong lrinh dao d6ng ctia con ldc ld;
r: '6;
Girii: Phuong trinh ly dQ currg: s - s6.sitr(u,rt I q) c6: ,= ^l+=./2{ - J radls..rn = l' =l! =2crrr. Do tai
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thoi di6nr t:0, r,Ai o'vj tri cln bfng vd di theo chiAu du.ong n€n g:0 (ch* ii rp - -nlL trong lruong hop hiinr dao dQng ld hdm cosin). = s = 2sin(7i) (cm) : 2cos(7t * ni2) (cm).
- / r--/ ,-t t t''.- r /'
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