Tác dụng làm quay của lực. Momen lực

Home Lớp 8 Khoa học tự nhiên 8 - sách Kết nối tri thức Bài 18: Tác dụng làm quay của lực. Momen lựcBài tập trung bình

{"common":{"save":0,"post_id":"8940","level":2,"total":10,"point":10,"point_extra":0},"segment":[{"id":"9391","post_id":"8940","mon_id":"1159539","chapter_id":"1159793","question":"Trong trò ch\u01a1i b\u1eadp bênh, m\u1ed9t b\u1ea1n n\u1eb7ng h\u01a1n có th\u1ec3 cân b\u1eb1ng v\u1edbi b\u1ea1n nh\u1eb9 h\u01a1n n\u1ebfu:<\/p>","options":["A.<\/strong> B\u1ea1n n\u1eb7ng ng\u1ed3i g\u1ea7n tr\u1ee5c quay h\u01a1n.","B.<\/strong> B\u1ea1n nh\u1eb9 ng\u1ed3i g\u1ea7n tr\u1ee5c quay h\u01a1n.","C.<\/strong> C\u1ea3 hai ng\u1ed3i t\u1ea1i cùng kho\u1ea3ng cách.","D.<\/strong> Không cách nào cân b\u1eb1ng \u0111\u01b0\u1ee3c."],"correct":"1","level":"2","hint":"C\u1ea7n moment l\u1ef1c hai bên b\u1eb1ng nhau \u0111\u1ec3 cân b\u1eb1ng.<\/p>","answer":"\u0110áp án \u0111úng là:<\/strong> A. B\u1ea1n n\u1eb7ng ng\u1ed3i g\u1ea7n tr\u1ee5c quay h\u01a1n.<\/p>Gi\u1ea3i thích:<\/em> <\/p>B\u1ea1n n\u1eb7ng có l\u1ef1c l\u1edbn nên c\u1ea7n rút ng\u1eafn cánh tay \u0111òn \u0111\u1ec3 moment l\u1ef1c b\u1eb1ng bên còn l\u1ea1i.<\/p>","type":"choose","extra_type":"classic","time":"0","user_id":"132","test":"0","date":"2025-04-18 08:02:26","option_type":"txt","len":3},{"id":"9392","post_id":"8940","mon_id":"1159539","chapter_id":"1159793","question":"N\u1ebfu moment l\u1ef1c c\u1ee7a l\u1ef1c tác d\u1ee5ng nh\u1ecf h\u01a1n moment l\u1ef1c cân b\u1eb1ng, v\u1eadt s\u1ebd:<\/p>","options":["A.<\/strong> Quay \u0111\u1ec1u.","B.<\/strong> \u0110\u1ee9ng yên.","C.<\/strong> Quay theo chi\u1ec1u ng\u01b0\u1ee3c l\u1ea1i.","D.<\/strong> Quay nhanh d\u1ea7n \u0111\u1ec1u."],"correct":"3","level":"2","hint":"Khi m\u1ea5t cân b\u1eb1ng moment l\u1ef1c, v\u1eadt s\u1ebd quay theo chi\u1ec1u moment l\u1edbn h\u01a1n.<\/p>","answer":"\u0110áp án \u0111úng là:<\/strong> C. Quay theo chi\u1ec1u ng\u01b0\u1ee3c l\u1ea1i.<\/p>Gi\u1ea3i thích:<\/em><\/p>Moment nh\u1ecf không cân b\u1eb1ng v\u1edbi moment l\u1edbn h\u01a1n → v\u1eadt quay theo chi\u1ec1u moment l\u1edbn.<\/p>","type":"choose","extra_type":"classic","time":"0","user_id":"132","test":"0","date":"2025-04-18 08:04:21","option_type":"txt","len":2},{"id":"9393","post_id":"8940","mon_id":"1159539","chapter_id":"1159793","question":"Mu\u1ed1n moment l\u1ef1c gi\u1ea3m m\u1ed9t n\u1eeda mà gi\u1eef nguyên \u0111\u1ed9 l\u1edbn l\u1ef1c, ta ph\u1ea3i làm gì?<\/p>","options":["A.<\/strong> Gi\u1ea3m cánh tay \u0111òn m\u1ed9t n\u1eeda","B.<\/strong> T\u0103ng cánh tay \u0111òn g\u1ea5p \u0111ôi","C.<\/strong> Gi\u1eef nguyên m\u1ecdi th\u1ee9","D.<\/strong> T\u0103ng l\u1ef1c lên g\u1ea5p \u0111ôi"],"correct":"1","level":"2","hint":"$M$<\/span> ~ $d$<\/span> n\u1ebfu $F$<\/span> không \u0111\u1ed5i.<\/p>","answer":"\u0110áp án \u0111úng là:<\/strong> A. Gi\u1ea3m cánh tay \u0111òn m\u1ed9t n\u1eeda<\/p>Gi\u1ea3i thích:<\/em><\/p>\u0110\u1ec3 moment l\u1ef1c gi\u1ea3m m\u1ed9t n\u1eeda, c\u1ea7n gi\u1ea3m cánh tay \u0111òn còn m\u1ed9t n\u1eeda.<\/p>","type":"choose","extra_type":"classic","time":"0","user_id":"132","test":"0","date":"2025-04-18 08:07:02","option_type":"txt","len":2},{"id":"9394","post_id":"8940","mon_id":"1159539","chapter_id":"1159793","question":"D\u1ee5ng c\u1ee5 nào sau \u0111ây giúp t\u0103ng moment l\u1ef1c d\u1ec5 dàng nh\u1ea5t?<\/p>","options":["A.<\/strong> Tay \u0111òn dài","B.<\/strong> Tay \u0111òn ng\u1eafn","C.<\/strong> L\u1ef1c nh\u1ecf","D.<\/strong> L\u1ef1c song song tr\u1ee5c quay"],"correct":"1","level":"2","hint":"Cánh tay \u0111òn dài giúp t\u1ea1o moment l\u1edbn h\u01a1n v\u1edbi cùng l\u1ef1c.<\/p>","answer":"\u0110áp án \u0111úng là:<\/strong> A. Tay \u0111òn dài<\/p>Gi\u1ea3i thích:<\/em><\/p>Tay \u0111òn dài → cánh tay \u0111òn l\u1edbn → moment l\u1ef1c l\u1edbn → d\u1ec5 t\u1ea1o tác d\u1ee5ng quay h\u01a1n.<\/p>","type":"choose","extra_type":"classic","time":"0","user_id":"132","test":"0","date":"2025-04-18 08:14:26","option_type":"txt","len":2},{"id":"9395","post_id":"8940","mon_id":"1159539","chapter_id":"1159793","question":"Trong bi\u1ec3u th\u1ee9c tính moment l\u1ef1c $M=F.d$<\/span>, n\u1ebfu h\u01b0\u1edbng c\u1ee7a l\u1ef1c không vuông góc v\u1edbi cánh tay \u0111òn thì:<\/p>","options":["A.<\/strong> Moment l\u1ef1c t\u0103ng lên.","B.<\/strong> Moment l\u1ef1c không thay \u0111\u1ed5i.","C.<\/strong> Moment l\u1ef1c gi\u1ea3m \u0111i.","D.<\/strong> V\u1eadt không quay \u0111\u01b0\u1ee3c."],"correct":"3","level":"2","hint":"Moment l\u1ef1c hi\u1ec7u qu\u1ea3 nh\u1ea5t khi l\u1ef1c tác d\u1ee5ng vuông góc v\u1edbi cánh tay \u0111òn.<\/p>","answer":"\u0110áp án \u0111úng là:<\/strong> C. Moment l\u1ef1c gi\u1ea3m \u0111i.<\/p>Gi\u1ea3i thích:<\/em><\/p>N\u1ebfu l\u1ef1c không vuông góc thì ch\u1ec9 ph\u1ea7n vuông góc c\u1ee7a l\u1ef1c m\u1edbi gây moment → moment l\u1ef1c th\u1ef1c t\u1ebf s\u1ebd nh\u1ecf h\u01a1n.<\/p>","type":"choose","extra_type":"classic","time":"0","user_id":"132","test":"0","date":"2025-04-18 08:16:00","option_type":"txt","len":2},{"id":"9396","post_id":"8940","mon_id":"1159539","chapter_id":"1159793","question":"Khi cùng m\u1ed9t l\u1ef1c \u0111\u01b0\u1ee3c tác d\u1ee5ng \u1edf các \u0111i\u1ec3m khác nhau trên m\u1ed9t v\u1eadt quay, v\u1ecb trí nào s\u1ebd t\u1ea1o moment l\u1ef1c l\u1edbn nh\u1ea5t?<\/p>","options":["A.<\/strong> G\u1ea7n tr\u1ee5c quay.","B.<\/strong> \u1ede gi\u1eefa v\u1eadt.","C.<\/strong> Xa tr\u1ee5c quay nh\u1ea5t.","D.<\/strong> B\u1ea5t k\u1ef3 v\u1ecb trí nào c\u0169ng nh\u01b0 nhau."],"correct":"3","level":"2","hint":"Moment l\u1ef1c ph\u1ee5 thu\u1ed9c vào kho\u1ea3ng cách t\u1eeb tr\u1ee5c quay \u0111\u1ebfn giá c\u1ee7a l\u1ef1c.<\/p>","answer":"\u0110áp án \u0111úng là:<\/strong> C. Xa tr\u1ee5c quay nh\u1ea5t.<\/p>Gi\u1ea3i thích:<\/em><\/p>Càng xa tr\u1ee5c quay thì cánh tay \u0111òn càng l\u1edbn → moment l\u1ef1c l\u1edbn h\u01a1n.<\/p>","type":"choose","extra_type":"classic","time":"0","user_id":"132","test":"0","date":"2025-04-18 08:17:28","option_type":"txt","len":2},{"id":"9397","post_id":"8940","mon_id":"1159539","chapter_id":"1159793","question":"M\u1ed9t ng\u01b0\u1eddi dùng d\u1ee5ng c\u1ee5 b\u1ea9y \u0111\u1ec3 nâng v\u1eadt n\u1eb7ng. N\u1ebfu t\u0103ng chi\u1ec1u dài cánh tay \u0111òn lên g\u1ea5p \u0111ôi mà gi\u1eef nguyên l\u1ef1c, moment l\u1ef1c s\u1ebd:<\/p>","options":["A.<\/strong> Không thay \u0111\u1ed5i.","B.<\/strong> T\u0103ng g\u1ea5p \u0111ôi.","C.<\/strong> Gi\u1ea3m m\u1ed9t n\u1eeda.","D.<\/strong> T\u0103ng g\u1ea5p b\u1ed1n l\u1ea7n."],"correct":"2","level":"2","hint":"Moment l\u1ef1c t\u1ec9 l\u1ec7 thu\u1eadn v\u1edbi chi\u1ec1u dài cánh tay \u0111òn.<\/p>","answer":"\u0110áp án \u0111úng là:<\/strong> B. T\u0103ng g\u1ea5p \u0111ôi.<\/p>Gi\u1ea3i thích:<\/em><\/p>N\u1ebfu gi\u1eef nguyên l\u1ef1c, mà t\u0103ng cánh tay \u0111òn g\u1ea5p \u0111ôi → moment l\u1ef1c c\u0169ng t\u0103ng g\u1ea5p \u0111ôi.<\/p>","type":"choose","extra_type":"classic","time":"0","user_id":"132","test":"0","date":"2025-04-18 08:18:42","option_type":"txt","len":2},{"id":"9398","post_id":"8940","mon_id":"1159539","chapter_id":"1159793","question":"M\u1ed9t ng\u01b0\u1eddi dùng tua vít \u0111\u1ec3 m\u1edf m\u1ed9t chi\u1ebfc n\u1eafp h\u1ed9p. \u0110i\u1ec1u nào sau \u0111ây giúp ng\u01b0\u1eddi \u0111ó m\u1edf d\u1ec5 h\u01a1n?<\/p>","options":["A.<\/strong> Tác d\u1ee5ng l\u1ef1c càng g\u1ea7n tr\u1ee5c xoay.","B.<\/strong> Tác d\u1ee5ng l\u1ef1c theo ph\u01b0\u01a1ng song song v\u1edbi tr\u1ee5c.","C.<\/strong> Tác d\u1ee5ng l\u1ef1c vuông góc và càng xa tr\u1ee5c xoay.","D.<\/strong> Dùng l\u1ef1c theo b\u1ea5t k\u1ef3 ph\u01b0\u01a1ng nào."],"correct":"3","level":"2","hint":"T\u0103ng moment l\u1ef1c b\u1eb1ng cách t\u0103ng cánh tay \u0111òn và gi\u1eef góc vuông.<\/p>","answer":"\u0110áp án \u0111úng là:<\/strong> C. Tác d\u1ee5ng l\u1ef1c vuông góc và càng xa tr\u1ee5c xoay.<\/p>Gi\u1ea3i thích:<\/em><\/p>Tác d\u1ee5ng l\u1ef1c càng xa tr\u1ee5c và vuông góc v\u1edbi tay c\u1ea7m giúp t\u1ea1o moment l\u1edbn → d\u1ec5 xoay.<\/p>","type":"choose","extra_type":"classic","time":"0","user_id":"132","test":"0","date":"2025-04-18 08:19:53","option_type":"txt","len":3},{"id":"9399","post_id":"8940","mon_id":"1159539","chapter_id":"1159793","question":"M\u1ed9t h\u1ecdc sinh dùng l\u1ef1c 25 N \u0111\u1ec3 m\u1edf m\u1ed9t cánh c\u1eeda có b\u1ea3n l\u1ec1. N\u1ebfu c\u1eeda không quay \u0111\u01b0\u1ee3c, nguyên nhân có th\u1ec3 là:<\/p>","options":["A.<\/strong> C\u1eeda quá n\u1eb7ng.","B.<\/strong> Cánh tay \u0111òn b\u1eb1ng 0 ho\u1eb7c l\u1ef1c không vuông góc.","C.<\/strong> L\u1ef1c tác d\u1ee5ng quá l\u1edbn.","D.<\/strong> B\u1ea3n l\u1ec1 b\u1ecb gãy."],"correct":"2","level":"2","hint":"Mu\u1ed1n v\u1eadt quay thì l\u1ef1c ph\u1ea3i t\u1ea1o \u0111\u01b0\u1ee3c moment l\u1ef1c khác 0.<\/p>","answer":"\u0110áp án \u0111úng là:<\/strong> B. Cánh tay \u0111òn b\u1eb1ng 0 ho\u1eb7c l\u1ef1c không vuông góc.<\/p>Gi\u1ea3i thích:<\/em><\/p>N\u1ebfu l\u1ef1c \u0111i qua tr\u1ee5c quay ho\u1eb7c không vuông góc thì cánh tay \u0111òn b\u1eb1ng 0 → moment l\u1ef1c b\u1eb1ng 0 → v\u1eadt không quay.<\/p>","type":"choose","extra_type":"classic","time":"0","user_id":"132","test":"0","date":"2025-04-18 08:22:55","option_type":"txt","len":3},{"id":"9400","post_id":"8940","mon_id":"1159539","chapter_id":"1159793","question":"M\u1ed9t thanh g\u1ed7 dài 2 m có tr\u1ee5c quay \u1edf gi\u1eefa. Hai l\u1ef1c b\u1eb1ng nhau cùng tác d\u1ee5ng \u1edf hai \u0111\u1ea7u thanh, nh\u01b0ng ng\u01b0\u1ee3c chi\u1ec1u nhau. \u0110i\u1ec1u gì x\u1ea3y ra?<\/p>","options":["A.<\/strong> Thanh quay nhanh d\u1ea7n.","B.<\/strong> Thanh quay ch\u1eadm d\u1ea7n. \n ","C.<\/strong> Thanh không quay.","D.<\/strong> Thanh r\u01a1i xu\u1ed1ng."],"correct":"3","level":"2","hint":"Hai moment l\u1ef1c ng\u01b0\u1ee3c chi\u1ec1u nhau và b\u1eb1ng nhau.<\/p>","answer":"\u0110áp án \u0111úng là:<\/strong> C. Thanh không quay.<\/p>Gi\u1ea3i thích:<\/em><\/p>Hai l\u1ef1c t\u1ea1o hai moment b\u1eb1ng nhau nh\u01b0ng ng\u01b0\u1ee3c chi\u1ec1u → t\u1ed5ng moment b\u1eb1ng 0 → v\u1eadt không quay.<\/p>","type":"choose","extra_type":"classic","time":"0","user_id":"132","test":"0","date":"2025-04-18 08:31:31","option_type":"txt","len":2}]}