做匀速圆周运动的物体的向心力是恒定的还是变化的
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\u3000\u3000\u516c\u5f0f\uff1aF\u5411=mr\u03c9(2)=mv(2)/r=4\u03c0(2)mr/T(2)
\u3000\u3000*(2)\u6307\u7684\u662f\u524d\u9762\u4e00\u4e2a\u5b57\u7b26\u7684\u5e73\u65b9
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\u3000\u3000\u5300\u901f\u5706\u5468\u8fd0\u52a8\u7684\u901f\u5ea6\u548c\u52a0\u901f\u5ea6\uff0c\u867d\u7136\u5927\u5c0f\u5747\u4e0d\u53d8\uff0c\u4f46\u5b83\u4eec\u7684\u65b9\u5411\u5374\u65f6\u523b\u53d8\u5316\uff0e\u56e0\u6b64\uff0c\u5300\u901f\u5706\u5468\u8fd0\u52a8\u662f\u53d8\u901f\u8fd0\u52a8\uff0c\u800c\u4e14\u662f\u975e\u5300\u53d8\u901f\u8fd0\u52a8\uff0e
\u3000\u30002\uff0e\u5bf9\u5411\u5fc3\u529b\u7684\u8ba4\u8bc6\uff0e
\u3000\u3000\uff081\uff09\u5411\u5fc3\u529b\u662f\u4ece\u529b\u7684\u6548\u679c\u6765\u547d\u540d\u7684\uff0c\u56e0\u4e3a\u5b83\u4ea7\u751f\u6307\u5411\u5706\u5fc3\u7684\u52a0\u901f\u5ea6\uff0c\u6240\u4ee5\u79f0\u5b83\u4e3a\u5411\u5fc3\u529b\uff0e\u5b83\u4e0d\u662f\u5177\u6709\u786e\u5b9a\u6027\u8d28\u7684\u67d0\u79cd\u7c7b\u578b\u7684\u529b\uff0e\u76f8\u53cd\uff0c\u4efb\u4f55\u6027\u8d28\u7684\u529b\u90fd\u53ef\u4ee5\u4f5c\u4e3a\u5411\u5fc3\u529b\uff0e\u5b9e\u9645\u4e0a\u5b83\u53ef\u662f\u67d0\u79cd\u6027\u8d28\u7684\u4e00\u4e2a\u529b\uff0c\u6216\u67d0\u4e2a\u529b\u7684\u5206\u529b\uff0c\u8fd8\u53ef\u4ee5\u662f\u51e0\u4e2a\u4e0d\u540c\u6027\u8d28\u7684\u529b\u6cbf\u7740\u534a\u5f84\u6307\u5411\u5706\u5fc3\u7684\u5408\u5916\u529b\uff0e
\u3000\u3000\uff082\uff09\u5411\u5fc3\u529b\u4e3a\u4f55\u4e0d\u628a\u7269\u4f53\u62c9\u5411\u5706\u5fc3
\u3000\u3000\u505a\u5706\u5468\u8fd0\u52a8\u7684\u7269\u4f53\uff0c\u901f\u5ea6\u65b9\u5411\u65f6\u523b\u8981\u6539\u53d8\uff0c\u4e3a\u4e86\u6539\u53d8\u7269\u4f53\u901f\u5ea6\u7684\u65b9\u5411 \u9700\u8981\u4e00\u5b9a\u5927\u5c0f\u7684\u529b\uff0c\u800c\u5411\u5fc3\u529b\u7684\u5927\u5c0f\u6070\u597d\u5c31\u7b49\u4e8e\u6240\u9700\u8981\u7684\u529b\uff0c\u56e0\u800c\u5b83\u6ca1\u6709\u201c\u4f59\u529b\u201d\u628a\u7269\u4f53\u62c9\u5411\u5706\u5fc3\uff0e
\u3000\u30003\uff0e\u5300\u901f\u5706\u5468\u8fd0\u52a8\u548c\u975e\u5300\u901f\u5706\u5468\u8fd0\u52a8
\u3000\u3000\u5706\u5468\u8fd0\u52a8\u6309\u7167\u901f\u5ea6\u5927\u5c0f\u662f\u5426\u53d8\u5316\u53ef\u5206\u4e3a\u5300\u901f\u5706\u5468\u8fd0\u52a8\u548c\u975e\u5300\u901f\u5706\u5468\u8fd0\u52a8\u4e24\u7c7b\uff0e
\u3000\u3000\u505a\u5300\u901f\u5706\u5468\u8fd0\u52a8\u7684\u7269\u4f53\uff0c\u901f\u5ea6\u5927\u5c0f\u4e0d\u53d8\uff0c\u53ea\u662f\u65b9\u5411\u6539\u53d8\uff0c\u56e0\u6b64\u52a0\u901f\u5ea6\u603b\u662f\u6307\u5411\u5706\u5fc3\uff0c\u5176\u5927\u5c0f\u4e0d\u53d8\uff1b\u5408\u5916\u529b\u4ea6\u603b\u662f\u6307\u5411\u5706\u5fc3\uff0c\u5927\u5c0f\u4e0d\u53d8\uff0e
\u3000\u3000\u505a\u975e\u5300\u901f\u5706\u5468\u8fd0\u52a8\u7684\u7269\u4f53\uff0c\u901f\u5ea6\u65b9\u5411\u548c\u5927\u5c0f\u5747\u53d8\uff0c\u5b83\u9664\u4e86\u6709\u6307\u5411\u5706\u5fc3\u7684\u52a0\u901f\u5ea6\u5916\uff0c\u8fd8\u6709\u6cbf\u5207\u7ebf\u65b9\u5411\u7684\u52a0\u901f\u5ea6\uff0c\u6240\u4ee5\u5408\u52a0\u901f\u5ea6\u4e0d\u6307\u5411\u5706\u5fc3\uff0c\u6240\u53d7\u5408\u5916\u529b\u4e5f\u4e0d\u6307\u5411\u5706\u5fc3\u3002\u7269\u4f53\u7684\u5411\u5fc3\u52a0\u901f\u5ea6\u5927\u5c0fa=v^2/r\u968fv\u503c\u53d8\u5316\uff0c\u5411\u5fc3\u529ba\u968fF=ma\u503c\u53d8\u5316\uff0e\u4f8b\u5982\uff0c\u5c0f\u7403\u6cbf\u7ad6\u76f4\u5e73\u9762\u5185\u7684\u5149\u6ed1\u5706\u8f68\u9053\u8fd0\u52a8\uff0c\u5982\u56fe\u6240\u793a\uff0c\u7403\u4ece\u4e0a\u5411\u4e0b\u901a\u8fc7A\u70b9\u65f6\u7684\u53d7\u4e24\u4e2a\u529b\u4f5c\u7528\uff0c
\u3000\u3000\u5176\u4e2d\u91cd\u529bG\u65b9\u5411\u4e0eVa\u76f8\u540c\uff0c\u4f7f\u5c0f\u7403\u901f\u5ea6\u5927\u5c0f\u53d1\u751f\u53d8\u5316\uff0c\u8f68\u9053\u5f39\u529bN\u4e0eVa\u5782\u76f4\uff0c\u6307\u5411\u5706\u5fc3\uff0c\u4f7f\u5c0f\u7403\u901f\u5ea6\u65b9\u5411\u53d1\u751f\u53d8\u5316\uff0c\u5373\u63d0\u4f9b\u5c0f\u7403\u505a\u5706\u5468\u8fd0\u52a8\u7684\u5411\u5fc3\u529b\uff0c\u5408\u529bF\u4e0eVa\u6210\u4e00\u89d2\u5ea6\uff0c\u5e76\u4e0d\u6307\u5411\u5706\u5fc3
\u54c7\u697c\u4e0a\u8bf4\u5f97\u90fd\u592a\u590d\u6742\u4e86\uff0c\u6211\u6765\u4e2a\u901a\u4fd7\u7684\u5427\u3002
\u601d\u8def\u8fc7\u7a0b\uff1a 1. \u529b\u662f\u77e2\u91cf\uff0c \u6709 \u5927\u5c0f \u548c \u65b9\u5411
2. \u5982\u679c\u529b\u53d8\u5316\u4e86\uff0c \u90a3\u4e48\u5176\u4e2d\u4e00\u4e2a\u80af\u5b9a\u53d8\u5316\u4e86\u3002
3. \u5411\u5fc3\u529b\u5927\u5c0f\u6ca1\u53d8\uff0c \u53d8\u5f97\u662f\u65b9\u5411\u3002
4. \u4e00\u4e2a\u7269\u4f53\u505a \u5706\u5468\u8fd0\u52a8\u65f6\uff08 \u4e0d\u662f\u5300\u901f\uff09\uff0c \u5b83\u53d7\u529b\u65b9\u5411\u5e94\u8be5\u4e00\u76f4\u4e0e\u5706 \u76f8\u5207
5. \u4f46\u6709\u4e86\u5411\u5fc3\u529b\uff0c \u5b83\u53d7\u529b \u65b9\u5411\u4e0d\u548c\u5706\u76f8\u5207\u4e86\uff0c \u800c\u662f\u59cb\u7ec8\u6307\u5411 \u5706\u5fc3\uff01~ \u5c31\u53d8\u6210\u4e86 \u5300\u901f\u5706\u5468\u8fd0\u52a8\u3002
\u8981\u70b9\u5c31\u662f\uff1a \u529b\u7684\u65b9\u5411\uff0c\u59cb\u7ec8\u6307\u5411\u5706\u5fc3\uff0c \u770b\u4f3c\u6709\u2018 \u59cb\u7ec8\u2019 \u4e8c\u5b57\uff0c \u65b9\u5411\u4e0d\u53d8\uff0c \u4f46\u662f\u522b\u5fd8\u4e86\uff0c \u7269\u4f53 \u662f\u8fd0\u52a8\u7684\uff0c \u65e0\u8bba\u8fd0\u52a8\u5230 \u5706\u5468\u4e0a\u7684\u54ea\u4e2a \u4f4d\u7f6e\uff0c \u4ecd\u7136\u6307\u5411\u5706\u5fc3\uff0c \u8fd9\u4e0d\u5c31\u662f \u4e00\u76f4\u5728\u53d8\u561b\u3002
(*^__^*) \u563b\u563b\u2026\u2026 \u6709\u70b9\u56f0\u60d1\u7684\u3002 \u522b\u62c5\u5fc3\uff0c\u7422\u78e8\u7422\u78e8\u5c31\u61c2\u4e86~ \u52a0\u6cb9\uff01
因为向心力方向始终指向圆心，即向心力方向时刻改变，
而力是矢量，不论大小改变还是方向改变，力都发生改变，
所以说 做匀速圆周运动的物体的向心力是变化的 。
大小恒定，方向变化，如果只问变不变那就答 变
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