a r t a r n a r nt aaa r r r + = 2 2 22 n 2 t ) R v () dt dv (aaa +=+= KÕt luËn •a n =0 -> chuyÓn ®éng th¼ng •a t =0 -> chuyÓn ®éng cong ®Òu •a=0 -> chuyÓn ®éng th¼ng ®Òu R 1 ®é cong cña quÜ ®¹o 4. Mét sè d¹ng chuyÓn ®éng c¬ ®Æc biÖt 4.1. ChuyÓn ®éng th¼ng biÕn ®æi ®Òu: O M 0consta == n a r const dt dv aa t === ∫ +== 0 vatadtv ∫ +=+=⇒+== tv 2 at dt)vat(svat dt ds v 0 2 00 4.2. ChuyÓn ®éng trßn T¹i M: t T¹i M’: t’=t+Δt => OM quÐt Δθ O tΔ θ Δ =ω dt d t lim 0t θ = Δ θ Δ =ω →Δ π ω ==ν ω π = 2T 12 T ; v 2 -v 2 0 =2as θ Δ M M’ v vμ r r ω Quan hÖ gi÷a θΔ=Δ= .RsMM ( ω= Δ θ Δ = Δ Δ →Δ→Δ .R t .Rlim t s lim 0t0t ω = R.v Rv r r r × ω = ⇒ HÖ qu¶: 2 22 R R )R( R v ω= ω == n a Gia tèc gãc: T¹i ω r ,t ω r v r R r O Qui t¾c tam diÖn thuËn 2 2 dt d dt d t θ = ω = Δ ωΔ =β →Δ 0t lim ω Δ + ω = ω Δ + = r r r ',tt't T¹i M’: ω r v r R r O M t a r β r ω r v r R r O M t a r β r Qui t¾c tam diÖn thuËn dt d t lim 0t ω = Δ ω Δ =β →Δ r r r R r r r ×β= t a βθ=ω−ω ω+ β =θ ω + β = ω 2 t 2 t t 2 0 2 0 2 0 T−¬ngtùnh− trong chuyÓn ®éng th¼ng: 4.3. ChuyÓn ®éng víi gia tèc kh«ng ®æi O x y h max α 0y v r 0x v r 0 v r a x =0 a y =-g a r g dt dv 0 y −= = dt dv x gtsinvv cosv 0y 0 −α= α= x v Ph−¬ng tr×nh chuyÓn ®éng 2 gt t.sinvy t.cosv 2 0 0 −α= α =x M Ph−¬ng tr×nh quÜ ®¹o α −α= 22 0 2 cosv2 gx xtgy 4.4. Dao ®éng th¼ng ®iÒu hoμ )tcos(.A ϕ + ω = x TuÇn hoμn theo thêi gian: x(t)=x(t+nT) ω π = 2 T x 0 )tsin(.A ϕ+ωω−== dt dx v )tcos(.A 2 ϕ+ωω−=== 2 2 dt xd dt dv a ph−¬ng tr×nh dao ®éng