C\u00c2U H\u1eceI<\/strong><\/p>\n

C\u00e2u 1 (trang 43 sgk V\u1eadt L\u00ed 12 n\u00e2ng cao):<\/b>\u00a0V\u1ebd ba \u0111\u01b0\u1eddng bi\u1ec3u di\u1ec5n s\u1ef1 ph\u1ee5 thu\u1ed9c c\u1ee7a th\u1ebf n\u0103ng, \u0111\u1ed9ng n\u0103ng, c\u01a1 n\u0103ng c\u1ee7a v\u1eadt n\u0103ng dao \u0111\u1ed9ng \u0111i\u1ec1u h\u00f2a theo th\u1eddi gian treen c\u00f9ng m\u1ed9t \u0111\u1ed3 thi. N\u00f3i r\u00f5 trong kho\u1ea3ng th\u1eddi gian n\u00e0o th\u00ec s\u1ef1 chuy\u1ec3n h\u00f3a th\u1ebf n\u0103ng th\u00e0nh \u0111\u1ed9ng n\u0103ng v\u00e0 trong kho\u1ea3ng th\u1eddi gian n\u00e0o th\u00ec c\u00f3 s\u1ef1 chuy\u1ec3n h\u00f3a ng\u01b0\u1ee3c l\u1ea1i.<\/span><\/p>\n

L\u1eddi gi\u1ea3i:<\/b><\/p>\n

\u2013 Gi\u1ea3 s\u1eed b\u1ea3n \u0111\u1ea7u th\u1ebf n\u0103ng c\u1ef1c \u0111\u1ea1i, \u0111\u1ed9ng n\u0103ng b\u1eb1ng kh\u00f4ng.<\/p>\n

– T\u1eeb 0 \u0111\u1ebfn T\/4: th\u1ebf n\u0103ng bi\u1ebfn th\u00e0nh \u0111\u1ed9ng n\u0103ng.<\/p>\n

– T\u1eeb T\/4 \u0111\u1ebfn T\/2. \u0110\u1ed9ng n\u0103ng th\u00e0nh th\u1ebf n\u0103ng.<\/p>\n

C\u00e2u 2 (trang 43 sgk V\u1eadt L\u00ed 12 n\u00e2ng cao):<\/b>\u00a0Ch\u1ee9ng t\u1ecf r\u1eb1ng c\u01a1 n\u0103ng c\u1ee7a v\u1eadt n\u0103ng dao \u0111\u1ed9ng \u0111i\u1ec1u h\u00f2a b\u1eb1ng \u0111\u1ed9ng n\u0103ng c\u1ee7a n\u00f3 \u1edf v\u1ecb tr\u00ed c\u1ea7n b\u1eb1ng v\u00e0 th\u1ebf n\u0103ng c\u1ee7a n\u00f3 khi li \u0111\u1ed9 c\u1ef1c \u0111\u1ea1i.<\/span><\/p>\n

L\u1eddi gi\u1ea3i:<\/b><\/p>\n

C\u01a1 n\u0103ng c\u1ee7a v\u1eadt dao \u0111\u1ed9ng: W = W_{t<\/sub>\u00a0+ W\u0111<\/sub>\u00a0= 1\/2 kx^{2<\/sup>\u00a0+ \/2 k.A2<\/sup><\/p>\n}}

\u1ede v\u1ecb tr\u00ed c\u00e2n b\u1eb1ng W_{t<\/sub>\u00a0= 0 \u21d2 W = W\u0111<\/sub>\u00a0= 1\/2 mv^{2<\/sup>\u00a0= 1\/2 kA2<\/sup><\/p>\n}}

Khi li \u0111\u1ed9 c\u1ef1c \u0111\u1ea1i W_{\u0111<\/sub>\u00a0= 0 \u21d2 W = Wt<\/sub>\u00a0= 1\/2kx^{2<\/sup>\u00a0= 1\/2 kA2<\/sup><\/p>\n}}

B\u00c0I T\u1eacP<\/strong><\/p>\n

B\u00e0i 1 (trang 43 sgk V\u1eadt L\u00ed 12 n\u00e2ng cao):<\/b>\u00a0\u0110\u1ed9ng n\u0103ng c\u1ee7a dao \u0111\u1ed9ng \u0111i\u1ec1u h\u00f2a bi\u1ebfn \u0111\u1ed5i theo th\u1eddi gian<\/span><\/p>\n

A. theo m\u1ed9t h\u00e0m d\u1ea1ng sin<\/p>\n

B. tu\u1ea7n ho\u00e0n v\u1edbi chu k\u00ec T<\/p>\n

C. tu\u1ea7n ho\u00e0n v\u1edbi chu k\u00ec T\/2<\/p>\n

D. kh\u00f4ng \u0111\u1ed5i<\/p>\n

L\u1eddi gi\u1ea3i:<\/b><\/p>\n

Ch\u1ecdn C. tu\u1ea7n ho\u00e0n theo chu k\u00ec T\/2.<\/p>\n

B\u00e0i 2 (trang 43 sgk V\u1eadt L\u00ed 12 n\u00e2ng cao):<\/b>\u00a0M\u1ed9t v\u1eadt c\u00f3 kh\u1ed1i l\u01b0\u1ee3ng 750g dao \u0111\u1ed9ng v\u1edbi bi\u00ean \u0111\u1ed9 4 cm v\u00e0 chu k\u1ef3 T = 2s. T\u00ednh n\u0103ng l\u01b0\u1ee3ng c\u1ee7a dao \u0111\u1ed9ng.<\/span><\/p>\n

L\u1eddi gi\u1ea3i:<\/b><\/p>\n

<\/p>\n

B\u00e0i 3 (trang 43 sgk V\u1eadt L\u00ed 12 n\u00e2ng cao):<\/b>\u00a0T\u00ednh th\u1ebf n\u0103ng, \u0111\u1ed9ng n\u0103ng v\u00e0 c\u01a1 n\u0103ng c\u1ee7a con l\u1eafc \u0111\u01a1n \u1edf m\u1ed9t v\u00ed tr\u00ed b\u1ea5t k\u00ec (li \u0111\u1ed9 g\u00f3c \u03b1) v\u00e0 th\u1eed l\u1ea1i r\u1eb1ng c\u01a1 n\u0103ng kh\u00f4ng \u0111\u1ed5i chuy\u1ec3n \u0111\u1ed9ng.<\/span><\/p>\n

L\u1eddi gi\u1ea3i:<\/b><\/p>\n

a) T\u00ednh th\u1ebf n\u0103ng W_{t<\/sub>: Th\u1ebf n\u0103ng Wt<\/sub>\u00a0c\u1ee7a con l\u1eafc \u0111\u01a1n l\u00e0 th\u1ebf n\u0103ng c\u1ee7a v\u1eadt ch\u1ecbu t\u00e1c d\u1ee5ng c\u1ee7a tr\u1ecdng l\u1ef1c, n\u1ebfu ch\u1ecdn v\u1ecb tr\u00ed c\u00e2n b\u1eb1ng O l\u00e0m g\u1ed1c th\u00ec th\u1ebf n\u0103ng khi v\u1eadt \u1edf v\u1ecb tr\u00ed M (h\u00ecnh 2.9) l\u00e0 Wt<\/sub>\u00a0= \u03c9h = \u03c9(1-cos\u2061\u03b1) d\u00f9ng c\u00f4ng th\u1ee9c l\u01b0\u1ee3ng gi\u00e1c 1-cos\u2061\u03b1 = 2 sin^{2<\/sup>\u2061[\u03b1\/2] v\u00e0 ch\u00fa \u00fd r\u1eb1ng, n\u1ebfu \u03b1 nh\u1ecf th\u00ec sin\u03b1\/2 \u2248 \u03b1\/2 ta c\u00f3:<\/p>\n}}

<\/p>\n

Trong \u0111\u00f3 s = l\u03b1 l\u00e0 \u0111\u1ed9 d\u00e0i \u0111\u1ea1i \u0111\u1ed9 d\u00e0i \u0111\u1ea1i s\u1ed1 c\u1ee7a cung OM.<\/p>\n

b) T\u00ednh \u0111\u1ed9ng n\u0103ng W_{\u0111<\/sub><\/p>\n}

W_{\u0111<\/sub>\u00a0= 1\/2mv^{2<\/sup>\u00a0trong \u0111\u00f3 v l\u00e0 v\u1eadn t\u1ed1c c\u1ee7a v\u1eadt n\u0103ng \u1edf v\u1ecb tr\u00ed M, v\u1edbi s cho b\u1edfi:<\/p>\n}}

<\/p>\n

c) T\u00ednh c\u01a1 n\u0103ng W. ch\u00fa \u00fd r\u1eb1ng theo (3.25) th\u00ec \u03c9^{2<\/sup>\u00a0= g\/l, ta s\u1ebd c\u00f3:<\/p>\n}

<\/p>\n

v\u1edbi c\u00e1c g\u00f3c nh\u1ecf \u03b1, t\u1ee9c l\u00e0 v\u1edbi s_{o<\/sub>\u00a0\u226a l<\/p>\n}

Ta l\u1ea1i th\u1ea5y c\u01a1 n\u0103ng c\u1ee7a con l\u1eafc \u0111\u01a1n kh\u00f4ng \u0111\u1ed5i trong su\u1ed1t qu\u00e1 tr\u00ednh dao \u0111\u1ed9ng v\u00e0i t\u1ec9 l\u1ec7 v\u1edbi b\u00ecnh Ph\u01b0\u01a1ng bi\u00ean \u0111\u1ed9 s_{o<\/sub>^{2<\/sup>. K\u1ebft lu\u1eadn tr\u00ean v\u1ec1 s\u1ef1 b\u1ea3o to\u00e0n c\u01a1 n\u0103ng c\u1ee7a con l\u1eafc \u0111\u01a1n c\u00f3 th\u1ec3 suy ra ngay t\u1eeb t\u00ednh ch\u1ea5t c\u1ee7a tr\u1ecdng l\u1ef1c t\u1eafc d\u1ee5ng l\u00ean con l\u1eafc l\u00e0 l\u1ef1c th\u1ebf.<\/p>\n}}

B\u00e0i 4 (trang 43 sgk V\u1eadt L\u00ed 12 n\u00e2ng cao):<\/b>\u00a0D\u1ef1a v\u00e0o \u0111\u1ecbnh lu\u1eadt b\u1ea3o to\u00e0n c\u01a1 n\u0103ng, t\u00ednh:<\/span><\/p>\n

a) V\u1eadn t\u1ed1c c\u1ee7a v\u1eadt n\u0103ng trong con l\u1eafc l\u00f2 xo khi qua v\u1ecb tr\u00ed c\u00e2n b\u1eb1ng theo bi\u00ean \u0111\u1ed9 A.<\/p>\n

b) V\u1eadn t\u1ed1c c\u1ee7a con l\u1eafc con \u0111i qua v\u1ecb tr\u00ed c\u00e2n b\u1eb1ng theo bi\u00ean \u0111\u1ed9 g\u00f3c \u03b1_{o<\/sub><\/p>\n}

L\u1eddi gi\u1ea3i:<\/b><\/p>\n

T\u1eeb c\u00e2u h\u1ecfi suy ra: W = 1\/2 mv_{o<\/sub>^{2<\/sup>\u00a0= 1\/2kA2<\/sup><\/p>\n}}

v_{o<\/sub>\u00a0l\u00e0 v\u1eadn t\u1ed1c v\u1eadt n\u0103ng khi qua v\u1ecb tr\u00ed c\u00e2n b\u1eb1ng, \u0111\u00f3 c\u0169ng l\u00e0 v\u1eadn t\u1ed1c c\u1ef1c \u0111\u1ea1i.<\/p>\n}

<\/p>\n

N\u1ebfu mu\u1ed1n t\u00ednh v_{o<\/sub>\u00a0theo bi\u00ean \u0111\u1ed9 cung so<\/sub>\u00a0= l\u03b1o<\/sub><\/p>\n","protected":false},"excerpt":{"rendered":"}

C\u00c2U H\u1eceI C\u00e2u 1 (trang 43 sgk V\u1eadt L\u00ed 12 n\u00e2ng cao):\u00a0V\u1ebd ba \u0111\u01b0\u1eddng bi\u1ec3u di\u1ec5n s\u1ef1 ph\u1ee5 thu\u1ed9c c\u1ee7a th\u1ebf n\u0103ng, \u0111\u1ed9ng n\u0103ng, c\u01a1 n\u0103ng c\u1ee7a v\u1eadt n\u0103ng dao \u0111\u1ed9ng \u0111i\u1ec1u h\u00f2a theo th\u1eddi gian treen c\u00f9ng m\u1ed9t \u0111\u1ed3 thi. N\u00f3i r\u00f5 trong kho\u1ea3ng th\u1eddi gian n\u00e0o th\u00ec s\u1ef1 chuy\u1ec3n h\u00f3a th\u1ebf n\u0103ng th\u00e0nh […]<\/p>\n","protected":false},"author":3,"featured_media":25248,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_mi_skip_tracking":false,"tdm_status":"","tdm_grid_status":""},"categories":[1304],"tags":[1432,1431],"yoast_head":"\n