一辆汽车以36km/h的速度行驶在城市的平直街道上,因为前方路口出现红灯,司机在较远的地方开始刹车,刹车 汽车以36km/h的速度在平直路面上匀速行驶,由于驾驶员注意...
\u6709\u4e00\u8f86\u8f66\u5728\u5e73\u76f4\u8def\u9762\u4e0a\u6b63\u4ee536km/h\u7684\u901f\u5ea6\u671d\u8be5\u8def\u53e3\u505c\u8f66\u7ebf\u5300\u901f\u524d\u884c\uff0c\u5728\u8f66\u5934\u524d\u7aef\u79bb\u505c\u8f66\u7ebf70m\u5904\u53f8\u673a\u770b\u5230\u524d\u65b9...\u8be6\u89c1http://taoti.tl100.com/read-1184226.html
\uff081\uff0936km/h=10m/s\u9a7e\u9a76\u5458\u6ce8\u610f\u529b\u4e0d\u96c6\u4e2d\u65f6\u6c7d\u8f66\u884c\u9a76\u7684\u8ddd\u79bbx=v 0 t=10\u00d760m=600m\uff082\uff09\u6c7d\u8f66\u901f\u5ea6\u51cf\u4e3a\u96f6\u6240\u9700\u7684\u65f6\u95f4t= v 0 a = 10 5 s=2s \u5219\u5239\u8f66\u540e4s\u5185\u7684\u4f4d\u79fb\u7b49\u4e8e2s\u5185\u7684\u4f4d\u79fb\uff0e\u5219 x= v 0 2 2a = 100 10 m=10m \uff0e\u7b54\uff1a\uff081\uff09\u9a7e\u9a76\u5458\u6ce8\u610f\u529b\u4e0d\u96c6\u4e2d\u65f6\u6c7d\u8f66\u5300\u901f\u884c\u9a76\u7684\u8ddd\u79bb\u4e3a600m\uff0e\uff082\uff09\u5239\u8f664s\u540e\u6c7d\u8f66\u901a\u8fc7\u7684\u4f4d\u79fb10m\uff0e
由题意取初速度方向为正方向,则v0=36km/h=10m/s,加速度a=-5m/s2(1)根据速度时间关系汽车刹车后1s的速度大小为v1=v0+at=10+(-5)×1m/s=5m/s
(2)根据速度时间关系汽车刹车后停止运动的时间t=
0?v0 |
a |
0?10 |
?5 |
(3)因为4s大于汽车停车时间,故4s末汽车的速度为0.
答:(1)刹车1s后汽车的速度大小为5m/s;
(2)刹车2s后汽车停下来;
(3)刹车4s后汽车的速度大小为0.
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