{"id":1007,"date":"2021-10-08T13:00:57","date_gmt":"2021-10-08T13:00:57","guid":{"rendered":"https:\/\/www.vietlearn.org\/post\/?p=1007"},"modified":"2021-10-14T22:12:11","modified_gmt":"2021-10-14T15:12:11","slug":"van-toc-trung-binh-la-gi-van-toc-la-gi-kien-thuc-vat-ly-8","status":"publish","type":"post","link":"https:\/\/www.vietlearn.org\/kien-thuc\/van-toc-trung-binh-la-gi-van-toc-la-gi-kien-thuc-vat-ly-8\/","title":{"rendered":"V\u1eadn t\u1ed1c trung b\u00ecnh l\u00e0 g\u00ec? V\u1eadn t\u1ed1c l\u00e0 g\u00ec? Ki\u1ebfn th\u1ee9c v\u1eadt l\u00fd 8"},"content":{"rendered":"\n<p class=\"wp-block-paragraph\">Ghi ch\u00fa: T\u00e0i li\u1ec7u tr\u00edch d\u1eabn<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">V\u1eadn t\u1ed1c l\u00e0 m\u1ed9t trong nh\u1eefng ph\u1ea7n kh\u00f3 c\u1ee7a b\u00e0i t\u1eadp V\u1eadt L\u00fd 8. Ph\u1ea7n ki\u1ebfn th\u1ee9c chung v\u1ec1 v\u1eadn t\u1ed1c r\u1ea5t r\u1ed9ng. Trong \u0111\u00f3 c\u00e1ch t\u00ednh v\u1eadn t\u1ed1c trung b\u00ecnh l\u00e0 hay \u0111\u01b0\u1ee3c cho v\u00e0o c\u00e1c b\u00e0i t\u1eadp \u00e1p d\u1ee5ng nh\u1ea5t. C\u00e1c em <a href=\"https:\/\/www.vietlearn.org\" data-internallinksmanager029f6b8e52c=\"2\" title=\"Vietlearn\" rel=\"nofollow\">h\u1ecdc sinh<\/a> \u0111\u00e3 n\u1eafm r\u00f5 kh\u00e1i ni\u1ec7m c\u1ee7a v\u1eadn t\u1ed1c trung b\u00ecnh l\u1edbp 8 v\u00e0 c\u00e1c th\u00f4ng tin li\u00ean quan hay ch\u01b0a? B\u00e0i vi\u1ebft sau s\u1ebd gi\u00fap gi\u1ea3i \u0111\u00e1p t\u1ea5t c\u1ea3. C\u00f9ng b\u1eaft \u0111\u1ea7u ngay th\u00f4i.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">V\u1eadn t\u1ed1c l\u00e0 g\u00ec b\u1ea1n c\u00f3 bi\u1ebft?<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">V\u1eadn t\u1ed1c l\u00e0 g\u00ec?<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Kh\u00e1i ni\u1ec7m c\u1ee7a v\u1eadn t\u1ed1c<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">V\u1eadn t\u1ed1c \u0111\u01b0\u1ee3c bi\u1ebft \u0111\u1ebfn nh\u01b0 l\u00e0 m\u1ed9t \u0111\u1ea1i l\u01b0\u1ee3ng v\u1eadt l\u00fd. Ch\u00fang \u0111\u1ea1i di\u1ec7n cho c\u1ea3 t\u1ed1c \u0111\u1ed9 nhanh hay ch\u1eadm l\u1eabn h\u01b0\u1edbng c\u1ee7a chuy\u1ec3n \u0111\u1ed9ng. V\u1eadn t\u1ed1c \u0111\u01b0\u1ee3c x\u00e1c \u0111\u1ecbnh b\u1eb1ng th\u01b0\u01a1ng s\u1ed1 gi\u1eefa \u0111\u1ed9 d\u00e0i qu\u00e3ng \u0111\u01b0\u1eddng di chuy\u1ec3n c\u1ee7a v\u1eadt trong m\u1ed9t kho\u1ea3ng th\u1eddi gian nh\u1ea5t \u0111\u1ecbnh v\u1edbi kho\u1ea3ng th\u1eddi gian \u0111\u00f3.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">V\u1eadn t\u1ed1c \u1edf trong kh\u00e1i ni\u1ec7m n\u00e0y \u0111\u01b0\u1ee3c hi\u1ec3u l\u00e0 v\u1eadn t\u1ed1c d\u00e0i hay c\u00f2n \u0111\u01b0\u1ee3c g\u1ecdi l\u00e0 v\u1eadn t\u1ed1c tuy\u1ebfn t\u00ednh, kh\u00e1c v\u1edbi v\u1eadn t\u1ed1c g\u00f3c. Trong V\u1eadt L\u00fd, v\u1eadn t\u1ed1c l\u1edbp 8 \u0111\u01b0\u1ee3c bi\u1ec3u di\u1ec5n b\u1edfi vect\u01a1 (hay c\u00f2n \u0111\u01b0\u1ee3c hi\u1ec3u l\u00e0 \u201c\u0111o\u1ea1n th\u1eb3ng c\u00f3 h\u01b0\u1edbng\u201d).<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">C\u00f4ng th\u1ee9c t\u00ednh v\u1eadn t\u1ed1c c\u01a1 b\u1ea3n<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Ta c\u00f3, v\u1eadn t\u1ed1c trong chuy\u1ec3n \u0111\u1ed9ng th\u1eb3ng \u0111\u1ec1u \u0111\u01b0\u1ee3c x\u00e1c \u0111\u1ecbnh b\u1eb1ng c\u00f4ng th\u1ee9c: v = s\/t, C\u00f4ng th\u1ee9c n\u00e0y gi\u1ed1ng v\u1eadn t\u1ed1c trung b\u00ecnh.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Trong \u0111\u00f3:<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">v l\u00e0 v\u1eadn t\u1ed1c<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">s l\u00e0 qu\u00e3ng \u0111\u01b0\u1eddng v\u1eadt \u0111i \u0111\u01b0\u1ee3c<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">t th\u1eddi gian \u0111i h\u1ebft qu\u00e3ng \u0111\u01b0\u1eddng \u0111\u00f3<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">T\u1eeb c\u00f4ng th\u1ee9c t\u00ednh tr\u00ean, ta c\u00f3 th\u1ec3 t\u00ednh ra \u0111\u01b0\u1ee3c 2 \u0111\u1ea1i l\u01b0\u1ee3ng l\u00e0 qu\u00e3ng \u0111\u01b0\u1eddng v\u00e0 th\u1eddi gian.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">C\u00f4ng th\u1ee9c t\u00ednh qu\u00e3ng \u0111\u01b0\u1eddng khi bi\u1ebft \u0111\u01b0\u1ee3c v\u1eadn t\u1ed1c v\u00e0 th\u1eddi gian: s = v*t<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">C\u00f4ng th\u1ee9c t\u00ednh th\u1eddi gian khi bi\u1ebft \u0111\u01b0\u1ee3c v\u1eadn t\u1ed1c v\u00e0 qu\u00e3ng \u0111\u01b0\u1eddng: t = s\/v<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">\u0110\u01a1n v\u1ecb c\u1ee7a v\u1eadn t\u1ed1c<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">V\u1eadn t\u1ed1c \u0111\u01b0\u1ee3c t\u00ednh ra t\u1eeb th\u1eddi gian v\u00e0 qu\u00e3ng \u0111\u01b0\u1eddng. Do v\u1eady \u0111\u01a1n v\u1ecb v\u1eadn t\u1ed1c s\u1ebd ph\u1ee5 thu\u1ed9c v\u00e0o \u0111\u01a1n v\u1ecb c\u1ee7a \u0111\u1ed9 d\u00e0i v\u00e0 \u0111\u01a1n v\u1ecb c\u1ee7a th\u1eddi gian.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">V\u1edbi quy \u01b0\u1edbc chung, qu\u00e3ng \u0111\u01b0\u1eddng \u0111\u01b0\u1ee3c \u0111o b\u1eb1ng \u0111\u01a1n v\u1ecb m\u00e9t (m). Th\u1eddi gian \u0111\u01b0\u1ee3c \u0111o b\u1eb1ng \u0111\u01a1n v\u1ecb gi\u00e2y (s). Do v\u1eady, \u0111\u01a1n v\u1ecb v\u1eadt l\u00fd c\u1ee7a v\u1eadn t\u1ed1c s\u1ebd l\u00e0 m\/s.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">\u0110\u01a1n v\u1ecb v\u1eadn t\u1ed1c l\u00e0 g\u00ec?<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Ngo\u00e0i ra, t\u1ed1c \u0111\u1ed9 c\u00f2n \u0111\u01b0\u1ee3c t\u00ednh b\u1eb1ng nh\u1eefng \u0111\u01a1n v\u1ecb kh\u00e1c nh\u01b0 km\/h, m\/h, km\/s\u2026. Tr\u01b0\u1edbc khi b\u1eaft tay gi\u1ea3i c\u00e1c b\u00e0i t\u1eadp v\u1ec1 v\u1eadn t\u1ed1c, <a href=\"https:\/\/www.vietlearn.org\" data-internallinksmanager029f6b8e52c=\"2\" title=\"Vietlearn\" rel=\"nofollow\">h\u1ecdc sinh<\/a> c\u1ea7n ph\u1ea3i x\u00e1c \u0111\u1ecbnh xem c\u00e1c \u0111\u01a1n v\u1ecb c\u1ee7a th\u1eddi gian, qu\u00e3ng \u0111\u01b0\u1eddng \u0111\u00e3 v\u1ec1 c\u00f9ng 1 h\u1ec7 quy chi\u1ebfu hay ch\u01b0a. N\u1ebfu ch\u01b0a th\u00ec ph\u1ea3i ti\u1ebfn h\u00e0nh \u0111\u1ed5i \u0111\u01a1n v\u1ecb tr\u01b0\u1edbc khi th\u1ef1c hi\u1ec7n t\u00ednh to\u00e1n.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Quy \u01b0\u1edbc c\u00e1ch \u0111\u1ed5i \u0111\u01a1n v\u1ecb trong v\u1eadn t\u1ed1c nh\u01b0 sau:<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">1m\/s = 3,6 km\/h<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">1km\/h = 0.28 m\/s<\/p>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\"><p>T\u00ecm hi\u1ec3u th\u00eam v\u1ec1 kh\u00e1i ni\u1ec7m v\u00e0 c\u00f4ng th\u1ee9c t\u00ednh hi\u1ec7u \u0111i\u1ec7n th\u1ebf<\/p><p>T\u00ecm hi\u1ec3u v\u1ec1 c\u01b0\u1eddng \u0111\u1ed9 d\u00f2ng \u0111i\u1ec7n v\u00e0 c\u00e1c kh\u00e1i ni\u1ec7m li\u00ean quan<\/p><\/blockquote>\n\n\n\n<p class=\"wp-block-paragraph\">\u1ee8ng d\u1ee5ng c\u1ee7a v\u1eadn t\u1ed1c<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">\u0110\u1ec3 \u0111o \u0111\u1ed9 l\u1edbn c\u1ee7a v\u1eadn t\u1ed1c, ng\u01b0\u1eddi ta d\u00f9ng t\u1ed1c k\u1ebf. Thi\u1ebft b\u1ecb n\u00e0y \u0111\u01b0\u1ee3c \u00e1p d\u1ee5ng v\u00e0o cu\u1ed9c s\u1ed1ng th\u1ef1c t\u1ebf r\u1ea5t nhi\u1ec1u, v\u00ed d\u1ee5 nh\u01b0 m\u00e1y b\u1eafn t\u1ed1c \u0111\u1ed9 c\u1ee7a c\u00f4ng an giao th\u00f4ng\u2026<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">S\u1ef1 kh\u00e1c bi\u1ec7t gi\u1eefa v\u1eadn t\u1ed1c v\u00e0 t\u1ed1c \u0111\u1ed9<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Th\u1ef1c t\u1ebf, nhi\u1ec1u ng\u01b0\u1eddi cho r\u1eb1ng t\u1ed1c \u0111\u1ed9 l\u00e0 v\u1eadn t\u1ed1c. Ch\u00fang kh\u00f4ng c\u00f3 s\u1ef1 kh\u00e1c nhau. Suy ngh\u0129 \u0111\u00f3 l\u00e0 sai ho\u00e0n to\u00e0n. T\u1ed1c \u0111\u1ed9 l\u00e0 \u0111\u1ed9 l\u1edbn v\u00f4 h\u01b0\u1edbng c\u1ee7a m\u1ed9t vect\u01a1 v\u1eadn t\u1ed1c. Ch\u00fang ch\u1ec9 c\u00f3 th\u1ec3 bi\u1ec3u th\u1ecb t\u1ed1c \u0111\u1ed9 c\u1ee7a m\u1ed9t v\u1eadt khi v\u1eadt \u0111ang chuy\u1ec3n \u0111\u1ed9ng.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">V\u00ed d\u1ee5 c\u1ee5 th\u1ec3, m\u1ed9t \u00f4 t\u00f4 \u0111ang di chuy\u1ec3n v\u1edbi v\u1eadn t\u1ed1c t\u01b0\u01a1ng \u0111\u1ed1i 20km\/h. \u00d4 t\u00f4 \u0111ang di chuy\u1ec3n tr\u00ean \u0111\u01b0\u1eddng tr\u00f2n n\u00ean ch\u00fang c\u00f3 t\u1ed1c \u0111\u1ed9 kh\u00f4ng \u0111\u1ed5i. C\u00f2n v\u1eadn t\u1ed1c c\u1ee7a \u00f4 t\u00f4 s\u1ebd thay \u0111\u1ed5i b\u1edfi v\u00ec h\u01b0\u1edbng c\u1ee7a \u00f4 t\u00f4 c\u00f3 thay \u0111\u1ed5i. Khi \u00f4 t\u00f4 \u0111i h\u1ebft m\u1ed9t v\u00f2ng tr\u00f2n, t\u1ed1c \u0111\u1ed9 v\u1eabn s\u1ebd l\u00e0 20km\/h. C\u00f2n v\u1eadn t\u1ed1c c\u1ee7a n\u00f3 s\u1ebd v\u1ec1 0, b\u1edfi v\u00ec \u00f4 t\u00f4 quay tr\u1edf l\u1ea1i v\u1ecb tr\u00ed ban \u0111\u1ea7u.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">V\u1eadn t\u1ed1c trung b\u00ecnh l\u1edbp 8<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Kh\u00e1i ni\u1ec7m v\u00e0 c\u00f4ng th\u1ee9c<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">V\u1eadn t\u1ed1c trung b\u00ecnh x\u00e9t m\u1ed9t kho\u1ea3ng th\u1eddi gian nh\u1ea5t \u0111\u1ecbnh \u0111\u01b0\u1ee3c t\u00ednh b\u1eb1ng th\u01b0\u01a1ng s\u1ed1 gi\u1eefa qu\u00e3ng \u0111\u01b0\u1eddng v\u1eadt di chuy\u1ec3n \u0111\u01b0\u1ee3c trong kho\u1ea3ng th\u1eddi gian \u0111ang x\u00e9t v\u00e0 kho\u1ea3ng th\u1eddi gian \u0111\u00f3.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Th\u00f4ng tin v\u1eadn t\u1ed1c trung b\u00ecnh<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">C\u00f4ng th\u1ee9c v\u1eadn t\u1ed1c TB: vtb = S\/t<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Trong \u0111\u00f3:<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">S l\u00e0 qu\u00e3ng \u0111\u01b0\u1ee3c \u0111i \u0111\u01b0\u1ee3c<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">t l\u00e0 th\u1eddi gian \u0111\u1ec3 c\u00f3 th\u1ec3 \u0111i h\u1ebft \u0111\u01b0\u1ee3c qu\u00e3ng \u0111\u01b0\u1eddng \u0111\u00f3.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">M\u1ed9t s\u1ed1 b\u00e0i t\u1eadp v\u1ec1 v\u1eadn t\u1ed1c trung b\u00ecnh<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">B\u00e0i 1: M\u1ed9t xe \u0111ang chuy\u1ec3n \u0111\u1ed9ng t\u1eeb A v\u1ec1 B. Trong 0,75 qu\u00e3ng \u0111\u01b0\u1eddng \u0111\u1ea7u \u0111i \u0111\u01b0\u1ee3c, xe chuy\u1ec3n \u0111\u1ed9ng v\u1edbi v\u1eadn t\u1ed1c 36km\/h. Xe chuy\u1ec3n \u0111\u1ed9ng trong th\u1eddi gian 10 ph\u00fat, v\u1eadn t\u1ed1c 24km\/h trong qu\u00e3ng \u0111\u01b0\u1eddng c\u00f2n l\u1ea1i. V\u1eadn t\u1ed1c trung b\u00ecnh c\u1ee7a xe tr\u00ean c\u1ea3 qu\u00e3ng \u0111\u01b0\u1eddng AB l\u00e0 bao nhi\u00eau?<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">B\u00e0i 2: M\u1ed9t xe \u0111ang chuy\u1ec3n \u0111\u1ed9ng t\u1eeb A v\u1ec1 \u0111\u1ebfn B. \u1ede n\u1eeda \u0111\u1ea7u qu\u00e3ng \u0111\u01b0\u1eddng, v\u1eadn t\u1ed1c c\u1ee7a xe l\u00e0 v1= 40km\/h. \u1ede n\u1eeda sau c\u1ee7a qu\u00e3ng \u0111\u01b0\u1eddng, xe c\u00f3 v\u1eadn t\u1ed1c l\u00e0 v2=60km\/h. H\u1ecfi v trung b\u00ecnh tr\u00ean c\u1ea3 qu\u00e3ng \u0111\u01b0\u1eddng c\u1ee7a xe l\u00e0 bao nhi\u00eau?<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">B\u00e0i 3: M\u1ed9t xe \u0111ang chuy\u1ec3n \u0111\u1ed9ng t\u1eeb A v\u1ec1 B. \u1ede n\u1eeda th\u1eddi gian \u0111\u1ea7u xe c\u00f3 v\u1eadn t\u1ed1c l\u00e0 v1=60km\/h. \u1ede n\u1eeda th\u1eddi gian sau xe c\u00f3 v\u1eadn t\u1ed1c l\u00e0 v2=40km\/h. T\u00ednh v\u1eadn t\u1ed1c trung b\u00ecnh tr\u00ean c\u1ea3 qu\u00e3ng \u0111\u01b0\u1eddng AB c\u1ee7a xe.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">H\u01b0\u1edbng d\u1eabn gi\u1ea3i c\u00e1c d\u1ea1ng b\u00e0i t\u1eadp li\u00ean quan v\u1eadn t\u1ed1c trung b\u00ecnh<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">B\u00e0i 1: Ph\u01b0\u01a1ng ph\u00e1p gi\u1ea3i \u1edf b\u00e0i n\u00e0y kh\u00f4ng c\u00f3 g\u00ec ph\u1ee9c t\u1ea1p. \u0110\u00e2y l\u00e0 b\u00e0i t\u1eadp gi\u00fap cho c\u00e1c em <a href=\"https:\/\/www.vietlearn.org\" data-internallinksmanager029f6b8e52c=\"2\" title=\"Vietlearn\" rel=\"nofollow\">h\u1ecdc sinh<\/a> l\u00e0m quen v\u00e0 hi\u1ec3u h\u01a1n v\u1ec1 v trung b\u00ecnh. Th\u1ebf n\u00ean c\u00f4ng th\u1ee9c t\u00ednh to\u00e1n kh\u00e1 \u0111\u01a1n gi\u1ea3n. Khi t\u00ednh v trung b\u00ecnh tr\u00ean m\u1ed9t con \u0111\u01b0\u1eddng chung, c\u00e1c em t\u00ednh t\u1ec9 s\u1ed1 l\u00e0 S\/t.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">B\u00e0i 2: \u1ede b\u00e0i n\u00e0y \u0111\u00e3 c\u00f3 s\u1ef1 kh\u00e1c bi\u1ec7t v\u00e0 ph\u1ee9c t\u1ea1p h\u01a1n trong qu\u00e1 tr\u00ecnh t\u00ednh. C\u00e1c em h\u00e3y g\u1ecdi S l\u00e0 \u0111\u1ed9 d\u00e0i c\u1ee7a c\u1ea3 \u0111o\u1ea1n \u0111\u01b0\u1eddng n\u00e0y. Ti\u1ebfp theo, t\u00ednh t\u1ed5ng s\u1ed1 th\u1eddi gian theo v\u1eadn t\u1ed1c trung b\u00ecnh v\u00e0 c\u1ee7a S. Sau \u0111\u00f3, t\u00ednh t\u1ed5ng th\u1eddi gian theo S c\u00f9ng c\u00e1c v\u1eadn t\u1ed1c th\u00e0nh ph\u1ea7n. V\u00ec th\u1eddi gian trong c\u1ea3 2 c\u00e1ch t\u00ednh n\u00e0y l\u00e0 b\u1eb1ng nhau. Th\u1ebf n\u00ean c\u00e1c em c\u00f3 th\u1ec3 li\u00ean h\u1ec7 gi\u1eefa v\u1eadn t\u1ed1c c\u00e1c th\u00e0nh ph\u1ea7n v\u00e0 v\u1eadn t\u1ed1c trung b\u00ecnh.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">B\u00e0i 3: T\u01b0\u01a1ng t\u1ef1 v\u1edbi b\u00e0i 2. N\u1ebfu nh\u01b0 b\u00e0i 2 c\u00e1c em l\u1ea5y \u0111\u1ea1i l\u01b0\u1ee3ng chung l\u00e0 S. Th\u00ec \u1edf b\u00e0i n\u00e0y c\u00e1c em h\u00e3y t\u00ednh to\u00e1n theo t. \u0110\u1ea7u ti\u00ean, g\u1ecdi t l\u00e0 t\u1ed5ng c\u1ea3 th\u1eddi gian m\u00e0 v\u1eadt chuy\u1ec3n \u0111\u1ed9ng h\u1ebft tr\u00ean qu\u00e3ng \u0111\u01b0\u1eddng. Ti\u1ebfp theo, t\u00ednh t\u1ed5ng qu\u00e3ng \u0111\u01b0\u1eddng theo v trung b\u00ecnh v\u00e0 \u0111\u1ea1i l\u01b0\u1ee3ng t. Ti\u1ebfp t\u1ee5c t\u00ednh t\u1ed5ng c\u1ea3 qu\u00e3ng \u0111\u01b0\u1eddng theo t v\u00e0 c\u00e1c v\u1eadn t\u1ed1c th\u00e0nh ph\u1ea7n. Khi \u0111\u00f3, qu\u00e3ng \u0111\u01b0\u1eddng trong c\u1ea3 2 c\u00e1ch t\u00ednh \u0111\u1ec1u b\u1eb1ng nhau n\u00ean ta c\u00f3 th\u1ec3 d\u1ec5 d\u00e0ng li\u00ean h\u1ec7 \u0111\u01b0\u1ee3c c\u00e1c v\u1eadn t\u1ed1c th\u00e0nh ph\u1ea7n v\u00e0 v\u1eadn t\u1ed1c trung b\u00ecnh.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Gi\u1ea3i c\u00e1c b\u00e0i t\u1eadp v\u1eadn t\u1ed1c trung b\u00ecnh<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">B\u00e0i 1:<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">\u0110\u1ed9 d\u00e0i c\u1ee7a qu\u00e3ng \u0111\u01b0\u1eddng sau l\u00e0 S2 = t2.v2 = 24. 1\/6 = 4 (km).<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">\u0110\u1ed9 d\u00e0i c\u1ee7a qu\u00e3ng \u0111\u01b0\u1eddng \u0111\u1ea7u l\u00e0 S1 = 3S2 = 12 (km).<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">T\u1ed5ng \u0111\u1ed9 d\u00e0i c\u1ee7a qu\u00e3ng \u0111\u01b0\u1eddng AB l\u00e0 S = S1 + S2 = 12 + 4 = 16 (km).<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Th\u1eddi gian \u0111i h\u1ebft c\u1ea3 qu\u00e3ng \u0111\u01b0\u1eddng \u0111\u1ea7u l\u00e0 t1\u00ad = 12\/36 = 1\/3 (h)<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">T\u1ed5ng th\u1eddi gian \u0111i h\u1ebft c\u1ea3 qu\u00e3ng \u0111\u01b0\u1eddng AB l\u00e0 t = t1 + t2 = 1\/3 + 1\/6 = 1\/2 (h)<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">V trung b\u00ecnh s\u1ebd l\u00e0 v = S\/t = 16\/(1\/2) = 32 (km\/h)<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">B\u00e0i 2<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">\u0110\u1ea7u ti\u00ean, g\u1ecdi S l\u00e0 \u0111\u1ed9 d\u00e0i qu\u00e3ng \u0111\u01b0\u1eddng AB. Ta g\u1ecdi v l\u00e0 v\u1eadn t\u1ed1c trung b\u00ecnh c\u1ee7a xe \u0111i c\u1ea3 qu\u00e3ng \u0111\u01b0\u1eddng AB.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Th\u1eddi gian \u0111\u1ec3 \u0111i t\u1eeb A v\u1ec1 B l\u00e0 t = S\/v (1)<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">M\u1eb7t kh\u00e1c, theo \u0111\u1ec1 b\u00e0i ta c\u00f3 t = t1 + t2 = S\/2v1 + S\/2v2 = S\/2.40 + S\/2.60 (2)<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">T\u1eeb (1) v\u00e0 (2) t\u00ednh to\u00e1n ta c\u00f3: v = 48km\/h<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">B\u00e0i 3<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">G\u1ecdi t l\u00e0 t\u1ed5ng th\u1eddi gian xe chuy\u1ec3n \u0111\u1ed9ng t\u1eeb A v\u1ec1 B, v l\u00e0 v\u1eadn t\u1ed1c trung b\u00ecnh c\u1ee7a xe.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">\u0110\u1ed9 d\u00e0i qu\u00e3ng \u0111\u01b0\u1eddng AB l\u00e0: S = v.t (1)<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Theo b\u00e0i ta c\u00f3: S=S1+S2=50t<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">T\u01b0\u0300 (1) va\u0300 (2) ta c\u00f3 v.t = 50t<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Nh\u01b0 v\u1eady, \u0111\u00e1p \u00e1n v = 50km\/h<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">D\u1ea1ng b\u00e0i t\u1eadp v\u1eadn t\u1ed1c trung b\u00ecnh<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Tr\u00ean \u0111\u00e2y l\u00e0 nh\u1eefng th\u00f4ng tin ch\u00fang t\u00f4i mang \u0111\u1ebfn cho b\u1ea1n v\u1ec1 v\u1eadn t\u1ed1c, v\u1eadn t\u1ed1c trung b\u00ecnh. Tin r\u1eb1ng qua b\u00e0i vi\u1ebft n\u00e0y, c\u00e1c b\u1ea1n c\u00f3 th\u1ec3 hi\u1ec3u th\u00eam v\u1ec1 c\u00e1c kh\u00e1i ni\u1ec7m v\u00e0 d\u1ea1ng b\u00e0i. C\u00f2n r\u1ea5t nhi\u1ec1u th\u00f4ng tin th\u00fa v\u1ecb kh\u00e1c \u0111\u01b0\u1ee3c \u0111\u0103ng t\u1ea3i tr\u00ean website c\u1ee7a ch\u00fang t\u00f4i. V\u00ed d\u1ee5 b\u00e0i vi\u1ebft v\u1ec1 s\u01a1 \u0111\u1ed3 m\u1ea1ch \u0111i\u1ec7n chi\u1ec1u d\u00f2ng \u0111i\u1ec7n. \u0110\u00e2y \u0111\u1ec1u l\u00e0 nh\u1eefng ki\u1ebfn th\u1ee9c hay s\u1eed d\u1ee5ng, c\u00f3 th\u1ec3 d\u1ec5 d\u00e0ng \u00e1p d\u1ee5ng \u0111\u01b0\u1ee3c trong cu\u1ed9c s\u1ed1ng. Th\u1ebf n\u00ean b\u1ea1n \u0111\u1eebng b\u1ecf qua nh\u00e9.<\/p>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\"><p>Kh\u00e1m ph\u00e1 th\u00eam nh\u1eefng ch\u1ee7 \u0111\u1ec1 kh\u00e1c<\/p><\/blockquote>\n\n\n\n<p class=\"wp-block-paragraph\">T\u1ed1c \u0111\u1ed9 ph\u1ea3n \u1ee9ng h\u00f3a h\u1ecdc h\u00f3a 10 \u2013 l\u00fd thuy\u1ebft, ph\u01b0\u01a1ng ph\u00e1p gi\u1ea3i b\u00e0i t\u1eadp<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">L\u00e0m sao \u0111\u1ec3 gi\u00fap<\/p>\n\n\n\n\n\n\n","protected":false},"excerpt":{"rendered":"<p>Ghi ch\u00fa: T\u00e0i li\u1ec7u tr\u00edch d\u1eabn V\u1eadn t\u1ed1c l\u00e0 m\u1ed9t trong nh\u1eefng ph\u1ea7n kh\u00f3 c\u1ee7a b\u00e0i t\u1eadp V\u1eadt L\u00fd 8. Ph\u1ea7n ki\u1ebfn th\u1ee9c chung v\u1ec1 v\u1eadn t\u1ed1c r\u1ea5t r\u1ed9ng. Trong \u0111\u00f3 c\u00e1ch t\u00ednh v\u1eadn t\u1ed1c trung b\u00ecnh l\u00e0 hay \u0111\u01b0\u1ee3c cho v\u00e0o c\u00e1c b\u00e0i t\u1eadp \u00e1p d\u1ee5ng nh\u1ea5t. C\u00e1c em h\u1ecdc sinh \u0111\u00e3 n\u1eafm r\u00f5 [&hellip;]<\/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":[4,7],"tags":[],"class_list":["post-1007","post","type-post","status-publish","format-standard","hentry","category-trung-hoc","category-vat-ly"],"_links":{"self":[{"href":"https:\/\/www.vietlearn.org\/kien-thuc\/wp-json\/wp\/v2\/posts\/1007","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=1007"}],"version-history":[{"count":0,"href":"https:\/\/www.vietlearn.org\/kien-thuc\/wp-json\/wp\/v2\/posts\/1007\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.vietlearn.org\/kien-thuc\/wp-json\/wp\/v2\/media?parent=1007"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.vietlearn.org\/kien-thuc\/wp-json\/wp\/v2\/categories?post=1007"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.vietlearn.org\/kien-thuc\/wp-json\/wp\/v2\/tags?post=1007"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}