Tr\u00ean c\u00e1c cu\u1ed9c thi \u0111\u1ea5u \u0111i\u1ec1n kinh th\u01b0\u1eddng c\u00f3 \u0111\u01b0\u1eddng ch\u1ea1y 200 m.<\/p>\n\n\n\n
\u0110o\u1ea1n \u0111\u1ea7u c\u1ee7a c\u00e1c \u0111\u01b0\u1eddng \u0111ua n\u00e0y th\u01b0\u1eddng c\u00f3 d\u1ea1ng n\u1eeda h\u00ecnh tr\u00f2n. N\u1ebfu c\u00f3 s\u00e1u ng\u01b0\u1eddi ch\u1ea1y \u0111\u1ed3ng th\u1eddi th\u00ec h\u1ecd s\u1ebd xu\u1ea5t ph\u00e1t tr\u00ean s\u00e1u \u0111\u01b0\u1eddng \u0111ua kh\u00e1c nhau. \u0110i\u1ec3m kh\u1edfi \u0111\u1ea7u c\u1ee7a \u0111\u01b0\u1eddng ch\u1ea1y ngo\u00e0i v\u01b0\u1ee3t l\u00ean ph\u00eda tr\u01b0\u1edbc kh\u00e1 xa so v\u1edbi \u0111\u01b0\u1eddng ph\u00eda trong.<\/p>\n\n\n\n
T\u1ea1i sao v\u1eady? \u0110i\u1ec3m xu\u1ea5t ph\u00e1t n\u00e0y \u0111\u01b0\u1ee3c quy\u1ebft \u0111\u1ecbnh do \u0111\u00e2u?<\/p>\n\n\n\n
Ch\u00fang ta \u0111\u1ec1u bi\u1ebft gi\u1eefa chu vi \u0111\u01b0\u1eddng tr\u00f2n v\u00e0 \u0111\u01b0\u1eddng k\u00ednh c\u00f3 m\u1ed9t t\u1ec9 l\u1ec7 x\u00e1c \u0111\u1ecbnh, \u0111\u00f3 ch\u00ednh l\u00e0 s\u1ed1 \u03c0 (s\u1ed1 pi), s\u1ed1 \u03c0 c\u00f3 gi\u00e1 tr\u1ecb g\u1ea7n \u0111\u00fang l\u00e0 3,14. V\u00e0 chu vi c\u1ee7a \u0111\u01b0\u1eddng tr\u00f2n c\u00f3 \u0111\u1ed9 d\u00e0i g\u1ea5p 3,14 l\u1ea7n \u0111\u01b0\u1eddng k\u00ednh hay c\u0169ng b\u1eb1ng 6,28 l\u1ea7n b\u00e1n k\u00ednh c\u1ee7a v\u00f2ng tr\u00f2n \u0111\u00f3. V\u00e0 C \u2248 6,28 R (C l\u00e0 \u0111\u1ed9 d\u00e0i c\u1ee7a \u0111\u01b0\u1eddng chu vi, R l\u00e0 b\u00e1n k\u00ednh v\u00f2ng tr\u00f2n). N\u1ebfu b\u00e1n k\u00ednh t\u0103ng 1 m\u00e9t th\u00ec \u0111\u01b0\u1eddng chu vi t\u0103ng th\u00eam 6,28 m.<\/p>\n\n\n\n
Trong c\u00e1c \u0111\u01b0\u1eddng ch\u1ea1y \u0111ua, th\u00ec c\u00e1c \u0111\u01b0\u1eddng \u0111ua \u0111\u1ec1u r\u1ed9ng 1,2 m. Hai \u0111\u01b0\u1eddng \u0111ua c\u1ea1nh nhau c\u00f3 b\u00e1n k\u00ednh sai kh\u00e1c nhau 1,2 m, v\u00ec v\u1eady \u0111\u01b0\u1eddng ch\u1ea1y ngo\u00e0i d\u00e0i h\u01a1n \u0111\u01b0\u1eddng trong k\u1ec1 \u0111\u00f3 7,54 m. Theo ti\u00eau chu\u1ea9n chung, v\u00f2ng ch\u1ea1y ngo\u00e0i th\u01b0\u1eddng d\u00e0i 400 m, tr\u00ean \u0111\u01b0\u1eddng ch\u1ea1y \u0111ua 200 m, ng\u01b0\u1eddi ta ph\u1ea3i t\u00ednh th\u1ebf n\u00e0o \u0111i\u1ec3m k\u1ebft th\u00fac c\u00e1c \u0111\u01b0\u1eddng ph\u1ea3i n\u1eb1m tr\u00ean m\u1ed9t \u0111\u01b0\u1eddng th\u1eb3ng. Th\u00f4ng th\u01b0\u1eddng ng\u01b0\u1eddi ta b\u1ed1 tr\u00ed \u0111\u1ea7u \u0111\u01b0\u1eddng ch\u1ea1y l\u00e0 n\u1eeda cung tr\u00f2n (th\u01b0\u1eddng d\u00e0i kho\u1ea3ng 114 m) sau \u0111\u00f3 s\u1ebd nh\u1eadp v\u00e0o \u0111\u01b0\u1eddng th\u1eb3ng (kho\u1ea3ng 86 m). \u1ede ph\u1ea7n cong, \u0111\u01b0\u1eddng trong c\u00f9ng c\u00f3 b\u00e1n k\u00ednh 36 m, ng\u01b0\u1eddi ch\u1ea1y \u1edf \u0111\u01b0\u1eddng \u0111ua th\u1ee9 nh\u1ea5t th\u01b0\u1eddng xu\u1ea5t ph\u00e1t \u1edf \u0111i\u1ec3m c\u00e1ch v\u00f2ng trong l\u00e0 0,3m, n\u00ean \u0111\u1ed9 d\u00e0i th\u1ef1c t\u1ebf c\u1ee7a \u0111o\u1ea1n ch\u1ea1y v\u00f2ng l\u00e0 36,3 m x 3,14 \u2248 114 m. \u0110i\u1ec3m xu\u1ea5t ph\u00e1t c\u1ee7a m\u1ed7i v\u00f2ng ngo\u00e0i ph\u1ea3i d\u1ecbch l\u00ean ph\u00eda tr\u01b0\u1edbc kho\u1ea3ng 1,2 m x 3,14 = 3,77 m so v\u1edbi \u0111i\u1ec3m xu\u1ea5t ph\u00e1t c\u1ee7a v\u00f2ng trong. N\u1ebfu tr\u00ean \u0111\u01b0\u1eddng ch\u1ea1y c\u00f3 s\u00e1u \u0111\u01b0\u1eddng th\u00ec c\u00e1c \u0111i\u1ec3m xu\u1ea5t ph\u00e1t s\u1ebd h\u00ecnh b\u1eadc thang, \u0111i\u1ec3m xu\u1ea5t ph\u00e1t c\u1ee7a \u0111\u01b0\u1eddng ch\u1ea1y ngo\u00e0i c\u00f9ng s\u1ebd d\u1ecbch l\u00ean ph\u00eda tr\u01b0\u1edbc 18,85 m so v\u1edbi \u0111\u01b0\u1eddng ch\u1ea1y trong c\u00f9ng, nh\u1edd c\u00e1ch s\u1eafp x\u1ebfp n\u00e0y m\u00e0 \u0111\u00edch c\u1ee7a s\u00e1u \u0111\u01b0\u1eddng ch\u1ea1y s\u1ebd n\u1eb1m tr\u00ean c\u00f9ng m\u1ed9t \u0111\u01b0\u1eddng th\u1eb3ng. Hi\u1ec3u \u0111\u01b0\u1ee3c quy t\u1eafc n\u00e0y, khi chu\u1ea9n b\u1ecb s\u00e2n v\u1eadn \u0111\u1ed9ng n\u00f3i chung ng\u01b0\u1eddi ta ch\u1ec9 c\u1ea7n \u0111o \u0111\u01b0\u1eddng ch\u1ea1y trong c\u00f9ng d\u00e0i \u0111\u00fang 200 m, x\u00e1c \u0111\u1ecbnh \u0111i\u1ec3m xu\u1ea5t ph\u00e1t c\u1ee7a \u0111\u01b0\u1eddng trong c\u00f9ng, sau \u0111\u00f3 c\u00e1c \u0111i\u1ec3m xu\u1ea5t ph\u00e1t c\u1ee7a c\u00e1c v\u00f2ng ngo\u00e0i \u0111\u01b0\u1ee3c d\u1ecbch l\u00ean ph\u00eda tr\u01b0\u1edbc m\u1ed9t \u0111\u1ed9 d\u00e0i nh\u01b0 \u0111\u00e3 t\u00ednh tr\u00ean kia m\u00e0 kh\u00f4ng c\u1ea7n ph\u1ea3i \u0111o t\u1eebng \u0111\u01b0\u1eddng ch\u1ea1y.<\/p>\n\n\n\n
S\u1ee9c n\u1ed5i c\u1ee7a phao c\u1ee9u sinh b\u1eb1ng bao nhi\u00eau?<\/p>\n\n\n\n
Khi b\u1ea1n mang chi\u1ebfc phao c\u1ee9u sinh xinh x\u1eafn v\u00e0 vui v\u1ebb v\u1eaby v\u00f9ng trong n\u01b0\u1edbc b\u1ea1n c\u00f3 ngh\u0129 \u0111\u1ebfn \u0111i\u1ec1u n\u00e0y: S\u1ee9c n\u1ed5i c\u1ee7a phao c\u1ee9u sinh l\u00e0 bao nhi\u00eau?<\/p>\n\n\n\n
L\u00e0m th\u1ebf n\u00e0o \u0111\u1ec3 t\u00ecm \u0111\u01b0\u1ee3c c\u00e2u tr\u1ea3 l\u1eddi?<\/p>\n\n\n\n
Ph\u01b0\u01a1ng ph\u00e1p t\u1ed1i \u01b0u l\u00e0 d\u00f9ng c\u00e1c tri th\u1ee9c to\u00e1n h\u1ecdc \u0111\u1ec3 t\u00ednh to\u00e1n: t\u00ednh th\u1ec3 t\u00edch kh\u00ed c\u1ee7a phao c\u1ee9u sinh r\u1ed3i nh\u00e2n v\u1edbi kh\u1ed1i l\u01b0\u1ee3ng ri\u00eang c\u1ee7a n\u01b0\u1edbc tr\u1eeb \u0111i kh\u1ed1i l\u01b0\u1ee3ng c\u1ee7a phao, k\u1ebft qu\u1ea3 s\u1ebd l\u00e0 s\u1ee9c n\u1ed5i c\u1ee7a phao c\u1ee9u sinh.<\/p>\n\n\n\n
M\u1ecdi ng\u01b0\u1eddi \u0111\u1ec1u bi\u1ebft kh\u1ed1i l\u01b0\u1ee3ng ri\u00eang c\u1ee7a n\u01b0\u1edbc l\u00e0 1 g\/cm3 (t\u1ee9c 1 cm3 n\u1eb7ng 1 g). D\u01b0\u1edbi \u0111\u00e2y s\u1ebd gi\u1edbi thi\u1ec7u ph\u01b0\u01a1ng ph\u00e1p t\u00ednh th\u1ec3 t\u00edch c\u1ee7a phao c\u1ee9u sinh.<\/p>\n\n\n\n
Theo nh\u01b0 h\u00ecnh v\u1ebd, h\u00ecnh chi\u1ebfu ph\u1eb3ng c\u1ee7a v\u00f2ng c\u1ee9u sinh c\u00f3 t\u00e2m O, v\u00f2ng c\u1ee9u sinh c\u00f3 hai ti\u1ebft di\u1ec7n. Hai ti\u1ebft di\u1ec7n n\u00e0y \u0111\u1ec1u l\u00e0 h\u00ecnh elip trong \u0111\u00f3 c\u00f3 m\u1ed9t elip qua b\u1ed1n \u0111i\u1ec3m A, B, C, D. Trong to\u00e1n h\u1ecdc ng\u01b0\u1eddi ta g\u1ecdi AB l\u00e0 tr\u1ee5c d\u00e0i c\u1ee7a h\u00ecnh elip, CD l\u00e0 chi\u1ec1u cao c\u1ee7a v\u00f2ng c\u1ee9u sinh, \u0111\u00f3 ch\u00ednh l\u00e0 tr\u1ee5c ng\u1eafn c\u1ee7a h\u00ecnh elip; OA l\u00e0 \u0111\u01b0\u1eddng k\u00ednh trong c\u1ee7a phao c\u1ee9u sinh sau khi \u0111\u00e3 b\u01a1m kh\u00ed. Do \u0111\u00f3 ng\u01b0\u1eddi ta c\u00f3 th\u1ec3 t\u00ednh th\u1ec3 t\u00edch c\u1ee7a v\u00f2ng c\u1ee9u sinh theo c\u00f4ng th\u1ee9c: \u03c0 l\u00e0 s\u1ed1 pi v\u00e0 b\u1eb1ng 3,14, AB, CD, OA d\u1ec5 d\u00e0ng \u0111o \u0111\u01b0\u1ee3c sau khi phao \u0111\u00e3 \u0111\u01b0\u1ee3c b\u01a1m c\u0103ng. Ta th\u1eed t\u00ednh to\u00e1n l\u1ef1c n\u1ed5i cho m\u1ed9t phao c\u1ee9u sinh c\u1ee5 th\u1ec3. Tr\u00ean th\u1ecb tr\u01b0\u1eddng ng\u01b0\u1eddi ta th\u01b0\u1eddng b\u00e1n m\u1ed9t lo\u1ea1i phao c\u00f3 \u0111\u01b0\u1eddng k\u00ednh v\u00f2ng tr\u00f2n l\u1edbn (\u0111\u01b0\u1eddng k\u00ednh ngo\u00e0i) khi ch\u01b0a b\u01a1m kh\u00ed l\u00e0 65 cm, l\u00e0m b\u1eb1ng ch\u1ea5t d\u1ebbo. Sau khi b\u01a1m kh\u00ed \u0111o \u0111\u01b0\u1ee3c AB = 13 cm, CD = 12,5 cm. OA = 12 cm. Kh\u1ed1i l\u01b0\u1ee3ng c\u1ee7a phao l\u00e0 150 g. \u1ee9ng d\u1ee5ng c\u00f4ng th\u1ee9c n\u00eau tr\u00ean ta d\u1ec5 d\u00e0ng t\u00ednh \u0111\u01b0\u1ee3c V \u2248 14.835 cm3. Do \u0111\u00f3 lo\u1ea1i phao c\u1ee9u sinh n\u00e0y c\u00f3 l\u1ef1c n\u1ed5i l\u00e0 145.383N (N: \u0111\u01a1n v\u1ecb \u0111o l\u1ef1c, \u0111\u1ecdc l\u00e0 niut\u01a1n).<\/p>\n\n\n\n
L\u1ef1c n\u1ed5i n\u00e0y c\u00f3 gi\u1eef \u0111\u01b0\u1ee3c c\u01a1 th\u1ec3 ng\u01b0\u1eddi n\u1ed5i tr\u00ean m\u1eb7t n\u01b0\u1edbc kh\u00f4ng? C\u00f3 th\u1ec3, v\u00ec khi ng\u01b0\u1eddi ta ch\u00ecm v\u00e0o n\u01b0\u1edbc s\u1ebd ch\u1ecbu l\u1ef1c \u0111\u1ea9y c\u1ee7a n\u01b0\u1edbc b\u1eb1ng l\u1ef1c n\u1ed5i. B\u1ea1n h\u00e3y th\u1eed xem.<\/p>\n\n\n\n
T\u1eeb kho\u00e1: H\u00ecnh elip.<\/p>\n\n\n\n
<\/p>\n\n\n\n\n\n\n","protected":false},"excerpt":{"rendered":"
Tr\u00ean c\u00e1c cu\u1ed9c thi \u0111\u1ea5u \u0111i\u1ec1n kinh th\u01b0\u1eddng c\u00f3 \u0111\u01b0\u1eddng ch\u1ea1y 200 m. \u0110o\u1ea1n \u0111\u1ea7u c\u1ee7a c\u00e1c \u0111\u01b0\u1eddng \u0111ua n\u00e0y th\u01b0\u1eddng c\u00f3 d\u1ea1ng n\u1eeda h\u00ecnh tr\u00f2n. N\u1ebfu c\u00f3 s\u00e1u ng\u01b0\u1eddi ch\u1ea1y \u0111\u1ed3ng th\u1eddi th\u00ec h\u1ecd s\u1ebd xu\u1ea5t ph\u00e1t tr\u00ean s\u00e1u \u0111\u01b0\u1eddng \u0111ua kh\u00e1c nhau. \u0110i\u1ec3m kh\u1edfi \u0111\u1ea7u c\u1ee7a \u0111\u01b0\u1eddng ch\u1ea1y ngo\u00e0i v\u01b0\u1ee3t l\u00ean ph\u00eda tr\u01b0\u1edbc […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":"","_disable_autopaging":false},"categories":[15,9],"tags":[],"class_list":["post-7559","post","type-post","status-publish","format-standard","hentry","category-hoi-dap-khoa-hoc","category-toan-hoc"],"_links":{"self":[{"href":"https:\/\/www.vietlearn.org\/kien-thuc\/wp-json\/wp\/v2\/posts\/7559","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.vietlearn.org\/kien-thuc\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.vietlearn.org\/kien-thuc\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.vietlearn.org\/kien-thuc\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.vietlearn.org\/kien-thuc\/wp-json\/wp\/v2\/comments?post=7559"}],"version-history":[{"count":0,"href":"https:\/\/www.vietlearn.org\/kien-thuc\/wp-json\/wp\/v2\/posts\/7559\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.vietlearn.org\/kien-thuc\/wp-json\/wp\/v2\/media?parent=7559"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.vietlearn.org\/kien-thuc\/wp-json\/wp\/v2\/categories?post=7559"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.vietlearn.org\/kien-thuc\/wp-json\/wp\/v2\/tags?post=7559"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}