Cơ năng (nâng cao)

Home Lớp 9 Khoa học tự nhiên 9 - sách kết nối tri thức Bài 3: Cơ năngBài tập nâng cao

{"common":{"save":0,"post_id":"8304","level":3,"total":10,"point":10,"point_extra":0},"segment":[{"id":"9634","post_id":"8304","mon_id":"1159533","chapter_id":"1159535","question":"Trong m\u1ed9t h\u1ec7 kín (không có ma sát), c\u01a1 n\u0103ng c\u1ee7a m\u1ed9t v\u1eadt \u0111\u01b0\u1ee3c b\u1ea3o toàn. K\u1ebft lu\u1eadn nào sau \u0111ây là \u0111úng?<\/p>","options":["A. C\u01a1 n\u0103ng \u0111\u01b0\u1ee3c chia \u0111\u1ec1u gi\u1eefa \u0111\u1ed9ng n\u0103ng và th\u1ebf n\u0103ng.","B. \u0110\u1ed9ng n\u0103ng luôn l\u1edbn h\u01a1n th\u1ebf n\u0103ng.","C. S\u1ef1 thay \u0111\u1ed5i \u0111\u1ed9ng n\u0103ng luôn kèm theo s\u1ef1 thay \u0111\u1ed5i ng\u01b0\u1ee3c l\u1ea1i c\u1ee7a th\u1ebf n\u0103ng.","D. C\u01a1 n\u0103ng ch\u1ec9 t\u1ed3n t\u1ea1i \u1edf d\u1ea1ng th\u1ebf n\u0103ng khi v\u1eadt \u0111\u1ee9ng yên."],"correct":"3","level":"3","hint":"","answer":"\u0110áp án: C. S\u1ef1 thay \u0111\u1ed5i \u0111\u1ed9ng n\u0103ng luôn kèm theo s\u1ef1 thay \u0111\u1ed5i ng\u01b0\u1ee3c l\u1ea1i c\u1ee7a th\u1ebf n\u0103ng. Gi\u1ea3i thích: Trong h\u1ec7 kín, khi c\u01a1 n\u0103ng \u0111\u01b0\u1ee3c b\u1ea3o toàn, n\u1ebfu \u0111\u1ed9ng n\u0103ng t\u0103ng (do v\u1eadn t\u1ed1c t\u0103ng), thì th\u1ebf n\u0103ng gi\u1ea3m (do \u0111\u1ed9 cao gi\u1ea3m), và ng\u01b0\u1ee3c l\u1ea1i.<\/p>","type":"choose","extra_type":"classic","time":"0","user_id":"125","test":"0","date":"2025-01-09 23:37:33","option_type":"txt","len":3},{"id":"9635","post_id":"8304","mon_id":"1159533","chapter_id":"1159535","question":"M\u1ed9t v\u1eadt \u0111ang dao \u0111\u1ed9ng trên m\u1ed9t qu\u1ef9 \u0111\u1ea1o. T\u1ea1i v\u1ecb trí th\u1ea5p nh\u1ea5t, \u0111i\u1ec1u nào sau \u0111ây là \u0111úng?<\/p>","options":["A. Th\u1ebf n\u0103ng \u0111\u1ea1t c\u1ef1c \u0111\u1ea1i, \u0111\u1ed9ng n\u0103ng b\u1eb1ng không.","B. \u0110\u1ed9ng n\u0103ng \u0111\u1ea1t c\u1ef1c \u0111\u1ea1i, th\u1ebf n\u0103ng b\u1eb1ng không.","C. C\u01a1 n\u0103ng c\u1ee7a v\u1eadt b\u1eb1ng không.","D. \u0110\u1ed9ng n\u0103ng và th\u1ebf n\u0103ng b\u1eb1ng nhau."],"correct":"2","level":"3","hint":"","answer":"\u0110áp án: B. \u0110\u1ed9ng n\u0103ng \u0111\u1ea1t c\u1ef1c \u0111\u1ea1i, th\u1ebf n\u0103ng b\u1eb1ng không.<\/p>Gi\u1ea3i thích:<\/p>\u1ede v\u1ecb trí th\u1ea5p nh\u1ea5t, \u0111\u1ed9 cao $h = 0$<\/span>, nên th\u1ebf n\u0103ng b\u1eb1ng không. V\u1eadn t\u1ed1c l\u1edbn nh\u1ea5t t\u1ea1i v\u1ecb trí này, làm \u0111\u1ed9ng n\u0103ng \u0111\u1ea1t c\u1ef1c \u0111\u1ea1i.<\/p>","type":"choose","extra_type":"classic","time":"0","user_id":"125","test":"0","date":"2025-01-10 21:48:12","option_type":"txt","len":3},{"id":"9636","post_id":"8304","mon_id":"1159533","chapter_id":"1159535","question":"M\u1ed9t qu\u1ea3 bóng l\u0103n xu\u1ed1ng t\u1eeb m\u1ed9t d\u1ed1c nghiêng. N\u1ebfu b\u1ecf qua ma sát, c\u01a1 n\u0103ng c\u1ee7a qu\u1ea3 bóng s\u1ebd: <\/p>","options":["A. Gi\u1ea3m d\u1ea7n khi qu\u1ea3 bóng l\u0103n.","B. Không \u0111\u1ed5i vì không có l\u1ef1c c\u1ea3n.","C. T\u0103ng d\u1ea7n khi qu\u1ea3 bóng l\u0103n.","D. B\u1eb1ng không khi qu\u1ea3 bóng \u0111\u1ea1t \u0111\u1ebfn \u0111áy d\u1ed1c."],"correct":"2","level":"3","hint":"","answer":"\u0110áp án: B. Không \u0111\u1ed5i vì không có l\u1ef1c c\u1ea3n.<\/p>Gi\u1ea3i thích:<\/p>B\u1ecf qua ma sát, h\u1ec7 qu\u1ea3 bóng - m\u1eb7t ph\u1eb3ng nghiêng là h\u1ec7 kín. Vì v\u1eady, c\u01a1 n\u0103ng (t\u1ed5ng \u0111\u1ed9ng n\u0103ng và th\u1ebf n\u0103ng) \u0111\u01b0\u1ee3c b\u1ea3o toàn, không \u0111\u1ed5i trong su\u1ed1t quá trình.<\/p>","type":"choose","extra_type":"classic","time":"0","user_id":"125","test":"0","date":"2025-01-10 21:50:59","option_type":"txt","len":3}]}