初二物理题！！急啊
\u521d\u4e8c\u7269\u7406\u9898\uff01\uff01\uff01\uff01\u6551\u6025\u5440\uff01\uff01\uff01\uff01\u8dea\u6c42\uff01\uff01\uff01\uff01\u4e24\u79cd\u60c5\u51b51\u3001\u81ea\u884c\u8f66\u5148\u8fc7\u3002\u4e34\u754c\u7684\u60c5\u51b5\u662f\u81ea\u884c\u8f66\u5c3e\u6b63\u597d\u4e0e\u6c7d\u8f66\u5934\u7684\u4e00\u7aef\uff08\u9760\u897f\u7684\u4e00\u7aef\uff09\u76f8\u4e92\u63a5\u89e6\uff0c\u90a3\u4e48\u6c7d\u8f66\u884c\u9a76\u7684\u65f6\u95f4\u4e3a\uff1at=s/v=12/20=0.6s\uff0c\u8fd9\u65f6\uff0c\u5bf9\u4e8e\u81ea\u884c\u8f66\u8d70\u8fc7\u7684\u8def\u7a0b\u81f3\u5c11\u4e3a\u81ea\u884c\u8f66\u957f+\u4e00\u534a\u7684\u9053\u5bbd+\u4e00\u822c\u7684\u6c7d\u8f66\u5bbd=4m\uff0c\u6240\u4ee5\u81ea\u884c\u8f66\u7684\u6700\u5c0f\u901f\u5ea6\u662f\uff1avmin=4/0.6=20/3m/s\uff0c\u6240\u4ee5\u81ea\u884c\u8f66\u7684\u901f\u5ea6\u5e94\u8be5\u226516/3m/s
2\u3001\u6c7d\u8f66\u5148\u8fc7\u3002\u4e34\u754c\u7684\u60c5\u51b5\u662f\u81ea\u884c\u8f66\u5934\u6b63\u597d\u4e0e\u6c7d\u8f66\u8f66\u4f4d\u7684\u4e00\u7aef\uff08\u9760\u4e1c\u7684\u4e00\u7aef\uff09\u76f8\u4e92\u63a5\u89e6\uff0c\u90a3\u4e48\u6c7d\u8f66\u884c\u9a76\u7684\u65f6\u95f4\u4e3a\uff1at=s/v=15/20=0.75s\uff0c\u8fd9\u65f6\uff0c\u5bf9\u4e8e\u81ea\u884c\u8f66\u8d70\u8fc7\u7684\u8def\u7a0b\u81f3\u591a\u4e3a\u9053\u5bbd\u7684\u4e00\u534a-\u6c7d\u8f66\u5bbd\u5ea6\u7684\u4e00\u534a=0.8m\uff0c\u6240\u4ee5\u81ea\u884c\u8f66\u7684\u6700\u5927\u901f\u5ea6\u662f\uff1avmax=0.8/0.75=16/15m/s\uff0c\u6240\u4ee5\u81ea\u884c\u8f66\u7684\u901f\u5ea6\u5e94\u8be5\u5c0f\u4e8e\u7b49\u4e8e16/15m/s
\u6240\u4ee5\u7efc\u4e0a\uff0cv\u5e94\u5927\u4e8e20/3m/s\u6216\u5c0f\u4e8e16/15m/s
\u5e0c\u671b\u80fd\u89e3\u51b3\u4f60\u7684\u95ee\u9898\uff0c\u6ee1\u610f\u8bf7\u91c7\u7eb3
\u7b54\u6848\uff1a\u5e94\u8be5\u52a0\u6c34\uff0c\u52a0\u6c34100g
\u89e3\u6790\uff1a
50\u6beb\u5347\uff1d50cm³
0.06kg=60g
\u76d0\u6c34\u7684\u5bc6\u5ea6\uff1a
\u03c1=m/v=60/50=1.2g/cm³\uff1e1.1g/cm³
\u6240\u4ee5\uff0c\u4e0d\u7b26\u5408\u8981\u6c42\uff0c\u5bc6\u5ea6\u5927\u4e86\uff0c\u5e94\u8be5\u52a0\u6c34\u3002
\u6807\u51c6\u76d0\u6c34\u7684\u5bc6\u5ea6\u03c1=1100kg/m³=1.1g/cm³
\u8bbe\u52a0\u6c34\u8d28\u91cf\u4e3am\uff0c\u52a0\u7684\u6c34\u4f53\u79ef\u4e3a\uff1bv=m/\u03c1\u6c34
\u603b\u8d28\u91cf\u4e3a\uff1a60\uff0bm\uff0c
\u603b\u4f53\u79ef\u4e3a\uff1a50+m/\u03c1\u6c34
\u03c1=\uff0860+m\uff09/(50+m/\u03c1\u6c34\uff09
1.1=\uff0860+m\uff09/(50+m/\u03c1\u6c34\uff09\uff0c\u03c1\u6c34\uff1d1g/cm3
\u89e3\u5f97\uff1am\uff1d50g
\u5373\uff0c50ml\u5e94\u8be5\u52a0\u6c3450g\uff0c100ml\u8981\u52a0\u6c34100g\u3002
冷却后盒内气体体积和水的体积都减小，造成气压降低，因而打不开（且发生形变）
用热水脚一下就好啦~
因为刚盖上时盒里有很多水蒸气（气体），冷了之后这些气体就没了（变成水珠），于是在大气压强的作用下，后面的就不用我说啦
水蒸气液化，饭盒内压强减小，导致大气压强大于盒内压强。
绛旓細(1) 鏍规嵁鏁堢巼=Gh/Fs锛宻=2h锛屽洜姝=F=G/鏁堢巼*2=2940/2/80%=1837.5(N)(2) 鎺掑紑0.1m3鐨勬按锛岄挗鍧楁墍鍙楁诞鍔涗负F娴=G鎺=1000N锛岃屽姩婊戣疆鐨勯噸涓1837.5*2-2940=735N锛岃繖鏃剁浉褰撲簬鎬诲叡闇鎷夎捣G'=2940-1000=1940N鐨勭墿浣擄紝鏁堢巼涓篏'/G'+G鍔=1940銆1940+735=72.5%锛屾眰鎷夊姏F锛氭牴鎹晥鐜=G'...
绛旓細1.宸茬煡锛氭苯杞︾殑閫熷害v1=12m/s 锛屽０闊崇殑閫熷害v2=340m/s锛屽徃鏈哄惉鍒板洖澹扮殑鏃堕棿 t=2s 姹傦細s3 瑙ｏ細鐢眝=s/t寰楋紝浠庢苯杞﹂福绗涘埌鍙告満鍚埌鍥為煶锛屾苯杞︾粡杩囩殑璺▼锛歴1=v1t=12m/s脳2s=24m 浠庢苯杞﹂福绗涘埌鍙告満鍚埌鍥為煶锛屽０闊崇粡杩囩殑璺▼锛歴2=v2t=340m/s脳2s=680m 姹借溅楦ｇ瑳澶勮窛楂樺北鐨勮窛绂籹3= (s1+ s2)/2...
绛旓細锛4锛夊鏋滃皢铚＄儧鍦ㄤ箼鍥剧殑鍩虹涓婅繙绂婚忛暅锛屼粛瑕佸湪鍏夊睆涓婂緱鍒版竻鏅扮殑鍍忥紝鍏夊睆搴斿悜闈犺繎锛堥夊～鈥滈潬杩戔濇垨鈥滆繙绂烩濓級閫忛暅鐨勬柟鍚戠Щ鍔紟鑰冪偣锛氬嚫閫忛暅鎴愬儚瑙勫緥鍙婂叾鎺㈢┒瀹為獙锛庝笓棰橈細瀹為獙棰橈紟鍒嗘瀽锛氾紙1锛夐氳繃鐢插浘鎵绀虹殑鐜拌薄锛岀粨鍚堝嚫閫忛暅鐒︾偣鐨勫畾涔夊嵆鍙‘瀹氳鍑搁忛暅鐨勭劍璺濓紟2锛夋帰绌跺嚫閫忛暅鎴愬儚鐨勫疄楠屾椂锛屽湪妗岄潰涓婁緷娆...
绛旓細褰撴湪鍧楅潤姝㈡椂鍗虫诞鍦ㄦ按闈笂锛岃繖鏄按瀵瑰簳闈㈢殑鍘嬪己鍗充负鏈ㄥ潡鐨勯噸鍔涘姞涓婃按鐨勯噸鍔涙瘮涓婂鍣ㄧ殑搴曢潰绉傛湪澶寸殑璐ㄩ噺涓0.3kg閲嶅姏涓簃g=3N锛屾按鐨勪綋绉负30*100-500cm^3=2500cm^3=0.0025m^3 姘寸殑璐ㄩ噺涓0.0025*1000kg=2.5kg 姘寸殑閲嶅姏涓2.5*10N=25N 鎬婚噸鍔涗负3+25=28N 鍘嬪己涓篎/S S=100cm...
绛旓細鐞嗘兂鎯呭喌涓嬶紝鑻ヤ笂涓嬩袱涓粦杞垎鍒负1鍜2锛屽垯G鐨勯噸鍔涜2鐨勪袱娈电怀瀛愬钩鍒嗭紝鍧囦负100N锛屽張琚1鐨勪袱娈电怀瀛愬钩鍒嗭紝鍧囦负50N锛屾墍浠=50N锛涜屽疄闄呬笂锛孎娈电Щ鍔20cm锛屽垯琚1鐨勪袱娈电怀瀛愬钩鍒嗭紝鍧囦负10cm锛屽張琚2鐨勪袱娈电怀瀛愬钩鍒嗭紝鍧囦负5cm锛屾晠閲嶇墿涓婂崌5cm G*h=200N*5cm=10W F*S=G*h/80%=10W/80%=12.5W=...
绛旓細瑙ｏ細宸茬煡锛歁鏉+M姘=600g M婧㈠嚭姘=200g P姘=1脳1000kg/m³ M鏉+M姘+M閲戝睘绮=900g 姹傦細V閲戝睘绮掑拰P閲戝睘绮 瑙ｏ細鏍规嵁瀵嗗害鍏紡p=m锛歷寰 棰樹腑婧㈠嚭姘200g m閲戝睘绮900g-600g=300g 鈭磛閲戝睘绮=V姘=200g梅1g/cm绔嬫柟 =200cm绔嬫柟 鍙堚埖m閲戝睘绮=300g v閲戝睘绮=200cm绔嬫柟 鈭磒...
绛旓細涓嶆噦璇疯拷闂 姹借溅鍦ㄧ灞卞礀700绫冲楦ｇ瑳锛屽０闊冲埌灞卞礀鎶樺洖锛屾姌鍥炶窛绂=700-40=660m锛屽０闊充紶鎾窛绂=700+660=1360m,鎴栬700m脳2-40=1360m 澹伴煶鍦ㄧ┖姘斾腑鐨勯熷害閫氬父鐢340m/绉掕绠 鍥犱负 s=vt 鎵浠 t=s/v=(700m脳2-40m)梅340m/绉 =1360m梅340m/绉 =4绉 鍙1鏃=3600绉 鎵浠=40绫趁4绉=...
绛旓細閲嶅姏A+閲嶅姏B=娑蹭綋瀵嗗害*800/1000000*10=0.008*娑蹭綋瀵嗗害 瀵逛簬閲戝睘A鏉ヨ锛氶噸鍔汚-娴姏A=鍘嬪姏=鏀寔鍔=2N 閲嶅姏A=鏀寔鍔+娴姏B=2+娑蹭綋瀵嗗害*10*800/5/1000000=2+0.0016*娑蹭綋瀵嗗害 瀵逛簬閲戝睘B鏉ヨ锛氶噸鍔汢=娴姏=800*3/5/1000000*10*娑蹭綋瀵嗗害=0.0048*娑蹭綋瀵嗗害 鎵浠ワ紙0.0048+0.0016锛*娑蹭綋瀵嗗害+2...
绛旓細鎸夐鍙锋暣鐞嗗涓 17銆1脳10^3锛屼竴绔嬫柟绫虫按鐨勮川閲忔槸1脳10^3鍗冨厠銆18銆佸乏 銆佸彸銆3.8 19銆0.0002銆0.28 20銆6 21銆侊紴 22銆7 23銆3锛2锛2锛3 24銆54 25銆4.86 26銆侊紙1锛夌墿浣撲笌鐮濈爜鏀鹃敊浜嗘墭鐩 锛2锛夌敤鎵嬫嬁鐮濈爜 27銆150锛117锛30锛1脳10^3 28銆侊紙1锛47.4 锛2锛変簩姝ワ細灏嗗皬鐡...
绛旓細U1/U2=R1/R0 6V/4V=3娆/R0 R0=2娆 褰撳紑鍏砈1銆丼2閮介棴鍚堟椂锛岀伅娉＄煭璺傛墍浠ョ數闃籖0娑堣楃殑鍔熺巼P=U^2/R=(10V)^2/2娆=50W === 缁堜簬鍋氬畬浜嗭紝杩欏嚑閬撻瓒宠冻30min鍟婏紒绁濅綘瀛︿範杩涙锛丳S:鏈変簺鐗╃悊閲忕殑瀛楁瘝鍙兘涓嶈鑼冿紝鍙傝冩椂娉ㄦ剰銆
