Lực đẩy Archimedes

Home Lớp 8 Khoa học tự nhiên 8 - sách Kết nối tri thức Bài 17: Lực đẩy ArchimedesBài tập trung bình

{"common":{"save":0,"post_id":"8637","level":2,"total":10,"point":10,"point_extra":0},"segment":[{"id":"9139","post_id":"8637","mon_id":"1159539","chapter_id":"1159710","question":"M\u1ed9t v\u1eadt có tr\u1ecdng l\u01b0\u1ee3ng 5 N khi \u0111\u1ec3 ngoài không khí. Khi th\u1ea3 chìm vào n\u01b0\u1edbc, l\u1ef1c \u0111\u1ea9y Archimedes tác d\u1ee5ng lên v\u1eadt là 2 N. Khi \u0111ó, tr\u1ecdng l\u01b0\u1ee3ng bi\u1ec3u ki\u1ebfn c\u1ee7a v\u1eadt trong n\u01b0\u1edbc là bao nhiêu?<\/p>","options":["A.<\/strong> 2 N","B.<\/strong> 3 N","C.<\/strong> 5 N","D.<\/strong> 7 N"],"correct":"2","level":"2","hint":"Tr\u1ecdng l\u01b0\u1ee3ng bi\u1ec3u ki\u1ebfn \u0111\u01b0\u1ee3c tính b\u1eb1ng tr\u1ecdng l\u01b0\u1ee3ng th\u1ef1c tr\u1eeb \u0111i l\u1ef1c \u0111\u1ea9y Archimedes.<\/p>","answer":"\u0110áp án \u0111úng là:<\/strong> B. 3 N<\/p>Gi\u1ea3i thích:<\/em><\/p>Tr\u1ecdng l\u01b0\u1ee3ng bi\u1ec3u ki\u1ebfn \u0111\u01b0\u1ee3c xác \u0111\u1ecbnh theo công th\u1ee9c: $P_{bi\u1ec3u\\ ki\u1ebfn}=P - F_A=5-2=3\\ N$<\/span><\/p>","type":"choose","extra_type":"classic","time":"0","user_id":"132","test":"0","date":"2025-03-31 12:11:46","option_type":"txt","len":0},{"id":"9140","post_id":"8637","mon_id":"1159539","chapter_id":"1159710","question":"Khi nhúng m\u1ed9t v\u1eadt hoàn toàn vào ch\u1ea5t l\u1ecfng, l\u1ef1c \u0111\u1ea9y Archimedes tác d\u1ee5ng lên v\u1eadt s\u1ebd thay \u0111\u1ed5i th\u1ebf nào n\u1ebfu ta chuy\u1ec3n v\u1eadt t\u1eeb n\u01b0\u1edbc sang d\u1ea7u (bi\u1ebft d\u1ea7u có kh\u1ed1i l\u01b0\u1ee3ng riêng nh\u1ecf h\u01a1n n\u01b0\u1edbc)?<\/p>","options":["A.<\/strong> L\u1ef1c \u0111\u1ea9y Archimedes gi\u1ea3m.","B.<\/strong> L\u1ef1c \u0111\u1ea9y Archimedes t\u0103ng.","C.<\/strong> L\u1ef1c \u0111\u1ea9y Archimedes không \u0111\u1ed5i.","D.<\/strong> Không xác \u0111\u1ecbnh \u0111\u01b0\u1ee3c."],"correct":"1","level":"2","hint":"L\u1ef1c \u0111\u1ea9y Archimedes ph\u1ee5 thu\u1ed9c vào kh\u1ed1i l\u01b0\u1ee3ng riêng c\u1ee7a ch\u1ea5t l\u1ecfng.<\/p>","answer":"\u0110áp án \u0111úng là:<\/strong> A. L\u1ef1c \u0111\u1ea9y Archimedes gi\u1ea3m.<\/p>Gi\u1ea3i thích:<\/em><\/p>L\u1ef1c \u0111\u1ea9y Archimedes tính theo công th\u1ee9c $F_A=dV$<\/span>. Khi v\u1eadt chìm hoàn toàn, th\u1ec3 tích chìm không \u0111\u1ed5i, nh\u01b0ng tr\u1ecdng l\u01b0\u1ee3ng riêng c\u1ee7a d\u1ea7u nh\u1ecf h\u01a1n n\u01b0\u1edbc nên l\u1ef1c \u0111\u1ea9y Archimedes gi\u1ea3m.<\/p>","type":"choose","extra_type":"classic","time":"0","user_id":"132","test":"0","date":"2025-03-31 12:14:28","option_type":"txt","len":2},{"id":"9141","post_id":"8637","mon_id":"1159539","chapter_id":"1159710","question":"M\u1ed9t v\u1eadt có kh\u1ed1i l\u01b0\u1ee3ng 1,2 kg, th\u1ec3 tích 1,5 $dm^3$<\/span>. Khi th\u1ea3 v\u1eadt vào n\u01b0\u1edbc, nó s\u1ebd nh\u01b0 th\u1ebf nào?<\/p>","options":["A.<\/strong> Chìm hoàn toàn.","B.<\/strong> N\u1ed5i m\u1ed9t ph\u1ea7n trên m\u1eb7t n\u01b0\u1edbc.","C.<\/strong> L\u01a1 l\u1eedng trong n\u01b0\u1edbc.","D.<\/strong> Không xác \u0111\u1ecbnh \u0111\u01b0\u1ee3c."],"correct":"2","level":"2","hint":"Xác \u0111\u1ecbnh l\u1ef1c \u0111\u1ea9y Archimedes và so sánh v\u1edbi tr\u1ecdng l\u01b0\u1ee3ng c\u1ee7a v\u1eadt.<\/p>","answer":"\u0110áp án \u0111úng là:<\/strong> B. N\u1ed5i m\u1ed9t ph\u1ea7n trên m\u1eb7t n\u01b0\u1edbc.<\/p>Gi\u1ea3i thích:<\/em><\/p>- Kh\u1ed1i l\u01b0\u1ee3ng riêng c\u1ee7a v\u1eadt: $\u03c1 = {m \\over V} ={1,2 \\over 1,5} =0,8\\ kg\/dm^3 =800\\ kg\/m^3$<\/span><\/p>- Kh\u1ed1i l\u01b0\u1ee3ng riêng c\u1ee7a n\u01b0\u1edbc: $1000\\ kg\/m^3$<\/span><\/p>- Vì $\u03c1_{v\u1eadt}<\u03c1_{n\u01b0\u1edbc}$<\/span> nên v\u1eadt s\u1ebd n\u1ed5i trên m\u1eb7t n\u01b0\u1edbc m\u1ed9t ph\u1ea7n.<\/p>","type":"choose","extra_type":"classic","time":"0","user_id":"132","test":"0","date":"2025-03-31 12:18:12","option_type":"txt","len":2}]}