初中物理压强题（需要详细过程，谢谢~）
\u521d\u4e2d\u7269\u7406\u538b\u5f3a\u9898\uff08\u9700\u8981\u8be6\u7ec6\u8fc7\u7a0b\uff091.\u9009B\u3002
\u516c\u5f0f\uff1aP = F / S\uff0c\u53d7\u529b\u5206\u6790\u53ef\u5f97\uff0c\u5728\u672a\u65bd\u52a0\u538b\u529bF\u524d\uff1a
\uff081\u4ee3\u8868\u7532\uff0c2\u4ee3\u8868\u4e59\uff09
P1 = G1 / S1\uff0cP2 = \uff08G1 + G2)/ S2
\u2235 P1 \uff1aP2 = 2 : 3
\u2234 2\uff08G\u7532 + G\u4e59)/ S\u4e59 = 3 G\u7532 / S\u7532
\u2234S1 = 3\uff08G1\u00b7S2\uff09/ 2\uff08G1 + G2\uff09
\u5f53\u65bd\u52a0\u4e86\u538b\u529bF\u540e\uff0c
P1' =\uff08G1 + F\uff09/ S1\uff0cP2' =\uff08G1 + G2 + F\uff09/ S2
\u628a\u538b\u529b\u65bd\u52a0\u524d\u6240\u5f97\u7684\u6bd4\u4f8b\u5173\u7cfb\u5f0f\u5e26\u5165\uff1a
P1' \uff1aP2' =\u30102(G1 + G2)(G1 + F) / 3G1\u00b7S2\u3011:\u3010\uff08G1 + G2 + F\uff09/ S2\u3011
\u6574\u7406\uff0c\u5f97\uff1aP1' \uff1aP2' = 2\uff08G1 + G2\uff09(G1 + F)/ 3G1\uff08G1 + G2 + F\uff09
\u3010\u5206\u6790\u3011\uff1a
P1' \uff1aP2' \u7684\u7ed3\u679c\u4e2d\u672a\u77e5\u6570\u5f88\u591a\u4e0d\u662f\u5e38\u6570\uff0c\u6240\u4ee5C\uff0cD\u76f4\u63a5\u6392\u9664\u3002
\uff1cA\uff1e \u5c06P1' \uff1aP2' = 1:3\u4ee3\u5165\u5f97\uff1a2(G1 + G2)(G1 + F) = G1(G1 + G2 + F)
\u6574\u7406\uff0c\u5f97\uff1aG1\uff08G1 + G2\uff09+ F\uff082 G2 + G1) = 0
\u56e0\u4e3a\u9898\u4e2d\u7684\u5df2\u77e5\u6761\u4ef6\u4e0e\u5b9e\u9645\u76f8\u8fde\u90fd\u662f\u6b63\u6570\uff0c\u65e0\u89e3\uff0c\u6240\u4ee5\u4e0d\u53ef\u80fd\u3002
\u6392\u9664\u6cd5\u7684\u8bdd\uff0c\u7b54\u6848\u5df2\u7ecf\u51fa\u6765\u4e86\uff0c\u4e0d\u8fc7B\u8fd8\u662f\u7ed9\u4f60\u5206\u6790\u4e0b\u5427\u3002
\uff1cB\uff1e \u5c06P1' \uff1aP2' = 1:1\u4ee3\u5165\u5f97\uff1a2(G1 + G2)(G1 + F)= 3G1(G1 + G2 + F)
\u6574\u7406\uff0c\u5f97\uff1aG1^2 + G1\u00b7G2 - F1\u00b7G1 - 2F\u00b7G2 = 0
\u6709\u52a0\u6709\u51cf\u6709\u6210\u7acb\u7684\u53ef\u80fd\uff0cB\u6761\u4ef6\u6210\u7acb\u3002
2.\u5443\u2026\u2026\u5173\u4e8e\u8fd9\u4e2a\u7ad6\u76f4\u65b9\u5411\u7684\u5207\u561b~~\u9664\u975e\u4e0d\u6539\u53d8\u5e95\u9762\u79ef\uff0c\u5426\u5219\u538b\u5f3a\u662f\u4e0d\u53d8\u7684\u3002
\u7531\u9898\u4e2d\u60c5\u51b5\uff0cP = G / S = mg / S = \u03c1Vg / S = \u03c1g\u00b7H
\u7531\u4ee5\u4e0a\u516c\u5f0f\uff0cm\u7684\u6539\u53d8\u8f6c\u5316\u6210\u4e86V\u7684\u6539\u53d8\uff0c\u800c\u7ad6\u76f4\u65b9\u5411\u7684\u5207\u5272\u5bfc\u81f4S\u4e5f\u968f\u7740V\u7684\u6539\u53d8\u800c\u53d8\uff0c\u6240\u4ee5\u6700\u540e\u7684\u7ed3\u679c\u5c31\u662f\u7ad6\u76f4\u5207\u5272\u4e0d\u6539\u53d8\u538b\u5f3a\u5927\u5c0f\u3002
\u4f1a\u6539\u53d8P\u7684\u539f\u56e0\uff0c\u53ea\u6709\u7269\u4f53\u7684\u9ad8H\u6709\u53d8\uff0c\u6216\u8005\u59824\u4e2d\u6240\u63cf\u8ff0\u7684\u60c5\u51b5\u2014\u2014m\u4e0d\u53d8S\u53d8
\u8fd9\u6837\u5206\u6790\uff0c1,2,3\u4e2d\u7684\u7ed3\u679c\u90fd\u662fP1 = P2 = P3\u3002
\u5982\u679c\u8981\u6b65\u9aa4\u7684\u8bdd\uff0c\u53ef\u4ee5\u5728\u8bd5\u5377\u4e0a\u5199\u51fa P = \u03c1g\u00b7H\u7684\u63a8\u5bfc\u5f0f\uff0c
\u7136\u540e\u5199\u51fa m , V , l \u7269\u7406\u91cf\u7684\u6539\u53d8\u4e0e P \u7684\u5927\u5c0f\u65e0\u5173\u5373\u53ef\u3002
\u53ea\u67094\uff0c\u9700\u8981\u989d\u5916\u5206\u6790\u3002
\u2463 \u2235P = \u03c1g\u00b7H\uff0cP1 = P2 = P3\uff0c\u4e14\u03c11 \uff1e \u03c12 \uff1e\u03c13
\u2234H1 \uff1c H2 \uff1c H3 \u2192 L1 \uff1c L2 \uff1c L3(L\u5e95\u9762\u8fb9\u957f\uff0c\u6b63\u65b9\u4f53\u561b\uff0cH = L)
\u5f53\u25b3L\u76f8\u7b49\u65f6\uff0cL\u8d8a\u5c0f\uff0c\u5e95\u9762\u79efS\u7684\u6539\u53d8\u767e\u5206\u6bd4\u5c31\u8d8a\u5927
(\u5c31\u50cf10\u5757\u94b1\u91cc\u4e22\u4e865\u5757\u94b1\uff0c\u548c50\u5757\u94b1\u91cc\u4e22\u4e865\u5757\u94b1\u7684\u611f\u89c9\u5dee\u4e0d\u591a)
\u8fd9\u6837\uff0c\u539f\u538b\u529b\u4e0d\u53d8\u800c\u4e09\u8005\u7684\u5e95\u9762\u79ef\u5374\u53d8\u5c0f\u4e86
\u2235\u25b3S1 \uff1e \u25b3S2 \uff1e \u25b3S3
\u2234P1 \uff1e P2 \uff1e P3
\u8fd9\u91cc\uff0c\u56e0\u4e3a\u4e09\u8005\u7684\u539f\u538b\u5f3a\u76f8\u7b49\uff0c\u6240\u4ee5\u5c31\u7528\u4ed6\u4eec\u73b0\u5728\u7684\u60c5\u51b5\u4e0e\u5176\u5404\u81ea\u4e4b\u524d\u7684\u60c5\u51b5\u76f8\u6bd4\u8f83\u65e7\u53ef\u4ee5\u4e86\uff0c\u6bd4\u8f83\u7684\u662f\u5404\u81ea\u7684\u6539\u53d8\u767e\u5206\u6bd4\uff0c\u800c\u4e0d\u662f\u76f4\u63a5\u7684\u7269\u7406\u91cf\u95f4\u6bd4\u8f83
\u67d0\u7535\u68af\u516c\u5bd3\u697c\u9ad8\u7ea640m\u5b8c\u6210\u6b64\u5efa\u7b51\u7269\u9700\u8981\u6d47\u5236\u94a2\u7b4b\u6df7\u51dd\u571f1\u00d7104m3\uff0c\u7528\u5176\u4ed6\u5efa\u7b51\u6750\u65993.5\u00d7104t\uff0c\u6df7\u51dd\u571f\u7684\u5bc6\u5ea6\u4e3a2.5\u00d7103kg/m3\uff0cg\u53d610N/kg\u3002
\uff081\uff09\u5df2\u77e5\u81ea\u6765\u6c34\u7684\u5bc6\u5ea6\u4e3a1\u00d7103kg/m3\uff0c\u82e5\u8981\u4ece\u5730\u9762\u5411\u697c\u9876\u63d0\u4f9b\u81ea\u6765\u6c34\uff0c\u52a0\u538b\u8bbe\u5907\u81f3\u5c11\u9700\u7ed9\u6c34\u65bd\u52a0\u591a\u5927\u7684\u538b\u5f3a\uff1f
\uff082\uff09\u6d4b\u91cf\u8868\u660e\uff0c\u8be5\u697c\u7684\u5730\u57fa\u6240\u627f\u53d7\u7684\u538b\u5f3a\u4e0d\u5f97\u8d85\u8fc71.2\u00d7106Pa\uff0c\u82e5\u623f\u57fa\u4e0e\u5730\u9762\u7684\u63a5\u89e6\u9762\u79ef\u4e3a1\u00d7103m2\uff0c\u5219\u6b64\u5927\u697c\u53e6\u5916\u6dfb\u52a0\u7684\u88c5\u9970\u6750\u6599\u3001\u5404\u79cd\u8bbe\u5907\u7b49\u7269\u8d28\u53ca\u8fdb\u5165\u5927\u697c\u7684\u4eba\u5458\u7684\u603b\u8d28\u91cf\u4e0d\u5f97\u8d85\u8fc7\u591a\u5c11
\u7b54\u6848 \uff081\uff09\u7531\u9898\u610f\u77e5\u52a0\u538b\u8bbe\u5907\u81f3\u5c11\u7ed9\u6c34\u65bd\u52a0\u7684\u538b\u5f3aP\u81f3\u5c11\u7b49\u4e8e40m\u9ad8\u6c34\u67f1\u4ea7\u751f\u7684\u538b\u5f3a\u3002
\u2234 P\u81f3\u5c11\uff1d\u03c1\u6c34gh\uff1d1\u00d7103kg/m3\u00d710N/kg\u00d740m\uff1d4\u00d7105Pa
\uff082\uff09\u8be5\u697c\u5730\u57fa\u627f\u53d7\u7684\u6700\u5927\u538b\u529b
F\u6700\u5927\uff1dP\u6700\u5927\u00b7S\uff1d1.2\u00d7106Pa\u00d71\u00d7103m2\uff1d1.2\u00d7109N
\u94a2\u7b4b\u6df7\u51dd\u571f\u91cd
G\u6df7\uff1d\u03c1\u6df7V\u6df7g\uff1d2.5\u00d7103kg/m3\u00d71\u00d7104m3\u00d710N/kg\uff1d2.5\u00d7108N
\u5176\u4ed6\u5efa\u7b51\u6750\u6599\u91cd
G\u5176\u4ed6\uff1dm\u5176\u4ed6\u00b7g\uff1d3.5\u00d7104\u00d7103kg\u00d710N/kg\uff1d3.5\u00d7108N
\u8bbe\u5927\u697c\u53e6\u5916\u6dfb\u52a0\u7684\u88c5\u9970\u6750\u6599\u3001\u5404\u79cd\u8bbe\u5907\u7b49\u7269\u8d28\u53ca\u8fdb\u5165\u5927\u697c\u7684\u4eba\u5458\u7684\u603b\u8d28\u91cf\u6700\u5927\u4e3am\u603b\uff0c\u7531\u9898\u77e5\uff1a
F\u6700\u5927\uff1dG\u6df7\uff0bG\u5176\u4ed6\uff0bm\u603bg
\u2234 1.2\u00d7109N\uff1d2.5\u00d7108N\uff0b3.5\u00d7108N+m\u603b\u00d710N/kg
\u2234 m\u603b\uff1d6\u00d7107kg.
\u5c0f\u660e\u7528\u4e00\u88c5\u6ee1\u7eaf\u51c0\u6c34\u7684\u74f6\u548c\u653e\u5728\u6c34\u5e73\u684c\u9762\u4e0a\u7684\u6d77\u7ef5\u505a\u5b9e\u9a8c\uff0c\u63a2\u7a76\u201c\u5f71\u54cd\u538b\u529b\u4f5c\u7528\u6548\u679c\u7684\u56e0\u7d20\u201d\u3002\u5982\u56fe\u6240\u793a\uff0c\u4ed6\u4ece\u5546\u6807\u4e0a\u67e5\u5230\u8fd9\u74f6\u6c34\u7684\u201c\u51c0\u542b\u91cf\u201d\u662f630mL\uff081mL=1cm3=10-6m3\uff09\uff1b\u53c8\u6d4b\u51fa\u74f6\u5e95\u9762\u79ef\u4e3a35cm2\uff0c\u74f6\u76d6\u9762\u79ef\u4e3a7cm2\uff0c\u7a7a\u74f6\u7684\u91cd\u529b\u5ffd\u7565\u4e0d\u8ba1\uff0c\u6839\u636e\u5c0f\u660e\u6536\u96c6\u7684\u6570\u636e\uff0c\u8bf7\u4f60\u8ba1\u7b97\uff1a
\uff081\uff09\u8fd9\u74f6\u7eaf\u51c0\u6c34\u51c0\u91cd\u591a\u5c11\uff1f
\uff082\uff09\u74f6\u5b50\u6b63\u653e\u65f6\u5bf9\u6d77\u7ef5\u7684\u538b\u5f3a\u662f\u591a\u5c11\uff1f
\uff083\uff09\u8981\u4f7f\u74f6\u5b50\u5012\u653e\u65f6\u5bf9\u6d77\u7ef5\u7684\u538b\u5f3a\u4e0e\u6b63\u653e\u65f6\u76f8\u540c\uff0c\u6700\u7b80\u5355\u7684\u65b9\u6cd5\u662f\u4ec0\u4e48\uff1f
\u7b54\u6848 1\uff09\u8fd9\u74f6\u7eaf\u51c0\u6c34\u7684\u8d28\u91cf\u4e3a\uff1a
m=\u03c1V=1.0\u00d7103\u00d7630\u00d710-6Kg=6.3N
\u5219\u8fd9\u74f6\u7eaf\u51c0\u6c34\u91cd\u4e3aG=mg=0.63\u00d710N=6.3N
\uff082\uff09\u74f6\u5b50\u5bf9\u6d77\u7ef5\u7684\u538b\u5f3a\u4e3a\uff1a
P=F/S=G/S=6.3/35\u00d710-4Pa=1.8\u00d7103Pa
\uff083\uff09\u8981P1=P2\u5373G/S1=G//S2\uff0cG/=GS2/S1=G/5\uff0c\u4e5f\u5c31\u662f\u8bf4\u5012\u653e\u540e\u74f6\u5b50\u4e2d\u53ea\u75591/5\u7684\u6c34\u5c31\u53ef\uff0c\u6545\u4ece\u74f6\u5b50\u4e2d\u5012\u51fa4/5\u7684\u6c34\u5c31\u53ef\u8fc7\u5230\u8981\u6c42\u3002
\uff08\u65b9\u6cd5\u4e8c\uff1a\u628a\u74f6\u5b50\u5012\u653e\u572835cm2\u7684\u5f88\u8f7b\u7684\u786c\u57ab\u7247\u4e0a\uff09
\u67d0\u540c\u5b66\u5728\u8584\u58c1\u5e73\u5e95\u8bd5\u7ba1\u4e2d\u88c5\u5165\u4e00\u4e9b\u6c99\u5b50\uff0c\u7ba1\u53e3\u5bc6\u5c01\uff0c\u5236\u6210\u4e00\u4e2a\u201c\u571f\u5bc6\u5ea6\u8ba1\u201d\u3002\u5f53\u628a\u5b83\u653e\u5165\u6c34\u4e2d\u7ad6\u76f4\u6f02\u6d6e\u65f6\uff0c\u8bd5\u7ba1\u9732\u51fa\u6c34\u9762\u7684\u9ad8\u5ea6\u4e3a5cm\uff1b\u5f53\u628a\u5b83\u653e\u5165\u67d0\u6db2\u4f53\u4e2d\u7ad6\u76f4\u6f02\u6d6e\u65f6\uff0c\u8bd5\u7ba1\u9732\u51fa\u6db2\u9762\u7684\u9ad8\u5ea6\u4e3a7cm\uff0e\u82e5\u8bd5\u7ba1\u548c\u6c99\u5b50\u7684\u603b\u8d28\u91cf\u4e3a30g\uff0c\u8bd5\u7ba1\u7684\u6a2a\u622a\u9762\u79ef\u4e3a1.5cm2\uff0c\u6c34\u7684\u5bc6\u5ea6\u4e3a1\u00d7103kg/m3\uff0e\u6c42\uff1a
\uff081\uff09\u8bd5\u7ba1\u5728\u6c34\u4e2d\u6f02\u6d6e\u65f6\u53d7\u5230\u7684\u6d6e\u529b\uff1b
\uff082\uff09\u5728\u6c34\u4e2d\u6f02\u6d6e\u65f6\uff0c\u6c34\u5bf9\u8bd5\u7ba1\u5e95\u90e8\u7684\u538b\u5f3a\uff1b
\uff083\uff09\u67d0\u6db2\u4f53\u7684\u5bc6\u5ea6\uff0e\uff08\u53d6g = 10N/kg\uff0c\u5c0f\u6570\u70b9\u540e\u4fdd\u7559\u4e24\u4f4d\u5c0f\u6570\uff09
\u7b54\u6848 \u89c1\u63d2\u56fe
\u5728\u5357\u6781\u8003\u5bdf\u4e2d\u4f7f\u7528\u7684\u6d77\u6d0b\u7834\u51b0\u8239\uff0c\u9488\u5bf9\u4e0d\u540c\u7684\u51b0\u5c42\u6709\u4e0d\u540c\u7684\u7834\u51b0\u65b9\u6cd5\u3002\u5176\u4e2d\u4e00\u79cd\u7834\u51b0\u7684\u65b9\u6cd5\u662f\uff1a\u63a5\u89e6\u51b0\u9762\u524d\uff0c\u8239\u5168\u901f\u822a\u884c\uff0c\u8239\u4f53\u5927\u90e8\u5206\u51b2\u4e0a\u51b0\u9762\uff0c\u5c31\u53ef\u4ee5\u628a\u51b0\u538b\u788e\u3002
\uff081\uff09\u5f53\u7834\u51b0\u8239\u822a\u884c\u4e8e\u6d77\u9762\u65f6\uff0c\u5b83\u7684\u6392\u6c34\u4f53\u79ef\u7ea6\u4e3a1500m3\uff0c\u6c42\u8239\u81ea\u8eab\u7684\u91cd\u529b\u3002\uff083\u5206\uff09
\uff082\uff09\u5728\u4e00\u6b21\u7834\u51b0\u884c\u52a8\u4e2d\uff0c\u5f53\u8239\u51b2\u5230\u51b0\u9762\u4e0a\u65f6\uff0c\u8239\u7684\u6392\u6c34\u4f53\u79ef\u53d8\u4e3a\u539f\u6765\u7684\u4e09\u5206\u4e4b\u4e00\uff0c\u8239\u4e0e\u51b0\u5c42\u63a5\u89e6\u9762\u79ef\u4e3a5m2\uff0c\u6b64\u65f6\u7834\u51b0\u8239\u5bf9\u51b0\u5c42\u7684\u538b\u5f3a\u662f\u591a\u5c11\uff1f\uff08\u6d77\u6c34\u7684\u5bc6\u5ea6\u53d61.0\u00d7103/m3\uff09
\u7b54\u6848 \uff081\uff09F\u6d6e=\u03c1\u6c34gV\u6392=103\u00d710\u00d71.5\u00d7103 N=1.5\u00d7107N \u56e0\u4e3a\u8239\u6f02\u6d6e\u6240\u4ee5 G= F\u6d6e=1.5\u00d7107N
\uff082\uff09F\u6d6e=1/3\u03c1\u6c34gV\u6392 (1\u5206) P=F/S=2G/3S=2\u00d7106Pa
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\u7b54\u6848 \u2474247.2N \u24754.25\u00d710-2m3
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\u7b54\u6848
2.73\u00d7103kg/m3
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\uff082\uff09\u82e5\u81ea\u884c\u8f66\u8d28\u91cf\u4e3a12kg\uff0c\u8f66\u80ce\u4e0e\u5730\u9762\u603b\u7684\u63a5\u89e6\u9762\u79ef\u4e3a40cm2\uff0c\u5219\u8be5\u540c\u5b66\u9a91\u8f66\u65f6\uff0c\u81ea\u884c\u8f66\u5bf9\u5730\u9762\u7684\u538b\u5f3a\u4e3a\u591a\u5c11\uff1f
\u7b54\u6848
\uff081) 200W (2\uff09 1.5\u00d710\u76845\u6b21\u65b9
设甲m1，s1，乙m2，s2
则m1/s1：(m1+m2)/s2=m1*s2/(m1+m2)*s1=2:3
加一个F力后，压强比为：
(m1+F)/S1:(m1+m2+F)/S2=(m1+F)*s2/(m1+m2+F)*s1
假设F=m1，则为2m1*s2/（m1+m2+m1）*s1>2m1*s2/2(m1+m2）*s1=2:3
当F无穷大时，(m1+F)*s2/(m1+m2+F)*s1>1,（可以忽略m1，m2而s1<s2)
取不一样的F可使得等于1:1。
1、沿竖直方向 切去等质量，问剩余部分对地面的压强
不管切掉多少，质量减少的比例和接触面积减少的比例一样，压强不会变化。对于甲乙丙来说，各自的压强不会变化，都和原来一样，还是相等。比如甲切掉一半，质量变成一半了，接触面积也变成一半了，压强还是不变。
2、沿竖直方向 切去等体积，问剩余部分对地面的压强
和上面一样，只要沿竖直切，不管切多少，压强都不变化，原来相等现在也相等。
3、沿竖直方向 切下等厚度，问剩余部分对地面的压强
切掉等厚度，面积不变，那么压强变成原来的比例都一样。因为质量变成原来的比例都一样。最后还是压强相等。
4、沿竖直方向 切下等厚度，再叠放在各自上方，问剩余部分对地面的压强
切掉了还放在上面质量等于没变，加上面积没变，压强也不变。
可以这么理解
加一个F，增加的压强就是δp=F/S
∵s甲<s乙
∴δp甲>δp乙
可以假设加F之前p甲=2k，p乙=3k
则加F后p甲：p乙
=2k+δp甲：3k+δp乙
>2k+δp乙：3k+δp乙
>2k:3k
所以选一个比2:3大的选项，是个不确定的值，不能选肯定
那就只能选B了
关于第二题:
因为是竖直方向切，无论怎么切都不影响他们各自对地面的压强，所以123题就是压强相等。
对于第4题，先根据密度关系是甲大于乙大于丙
得出体积甲<乙<丙
切去等厚度，那相对于三个立方体，甲切下来的部分占总体积的比例最大。
所以增加的压强来说甲大于乙大于丙
理解理解。
nb 2楼
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