2020年2月,在国际单板滑雪U型场地赛中,我国运动员蔡雪桐勇夺冠军。如图,滑道边缘线
的倾角
,运动员以速度
从
上的O点沿
的切面滑出滑道,滑出时速度方向与
的夹角为
,腾空后从
上的A点进入滑道。已知重力加速度为g,运动员可视为质点,不计空气阻力。求运动员:
(1)腾空中上升的最大高度;
(2)腾空中离
的最大距离;
(3)到达A点时的速度。
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7a5f1641947153c80b987320885a2b57.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/74dc2063147bb66cc18c7cab905bb662.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6f58888df91890a19a1aa7511d19703f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7a5f1641947153c80b987320885a2b57.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7a5f1641947153c80b987320885a2b57.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7a5f1641947153c80b987320885a2b57.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2d02d80d4e2f6f984036bd22a1a2077b.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7a5f1641947153c80b987320885a2b57.png)
(1)腾空中上升的最大高度;
(2)腾空中离
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7a5f1641947153c80b987320885a2b57.png)
(3)到达A点时的速度。
![](https://img.xkw.com/dksih/QBM/2021/10/14/2829409398030336/2830434460860416/STEM/ae08d99c-3d07-409f-8cd7-e7566ac3659d.png?resizew=528)
更新时间:2021-10-16 09:16:33
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解答题
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较难
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【推荐1】如图所示轨道由两个圆弧轨道与一倾斜轨道构成。一质量为
的物块压缩弹簧后从
点出发,经过长为
,动摩擦因数为
的粗糙轨道
后进入两段圆弧轨道,且圆弧半径满足
,物块进入轨道
后,在
点有一振波器,能使物块以与水平方向夹角为
的角度从
点飞出且速度大小保持不变,物块飞出后落在倾斜角为
的足够长的斜面
上。除
段粗糙外其余轨道均光滑,
,
,
,求:
(1)若物块在
点的速度为
,求物块在
点对轨道的压力;
(2)若物块全程不脱离圆弧轨道,求弹簧的弹性势能的最小值;
(3)弹簧弹性势能为
,若使物块在轨道
上方飞行时间最久,求
的值。
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3f1b1bd0f94ae786c99ded377c0e79a6.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5963abe8f421bd99a2aaa94831a951e9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/585c0b361a3e508f3dbb27a40b2dad5e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f89eef3148f2d4d09379767b4af69132.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f52a58fbaf4fea03567e88a9f0f6e37e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7392c1d532dd06e22fa80f6f3004770d.png)
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![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2a30f3a8b673cc28bd90c50cf1a35281.png)
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![](https://staticzujuan.xkw.com/quesimg/Upload/formula/49b50357a6545cae8348e3059312f520.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f52a58fbaf4fea03567e88a9f0f6e37e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f986badfc5dea707c164e2ab6c98dd06.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/fb8485466d2127bd681a322f87c58f86.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/67802092c4c9f3b1cff1f9502b7d1ded.png)
(1)若物块在
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7f9e8449aad35c5d840a3395ea86df6d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ebcc176a2056b2e036d83de9144cc21c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7f9e8449aad35c5d840a3395ea86df6d.png)
(2)若物块全程不脱离圆弧轨道,求弹簧的弹性势能的最小值;
(3)弹簧弹性势能为
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8574077ff224783e92bb68e6faf3763d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/49b50357a6545cae8348e3059312f520.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6cc9750c313ee972124cb62c4a6fb7ea.png)
![](https://img.xkw.com/dksih/QBM/2022/4/9/2954466500952064/2955777880793088/STEM/c3115077-7efa-4c98-bc70-980b3f2cad48.png?resizew=344)
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【推荐2】如图所示,在平面直角坐标系xOy内,第Ⅰ象限的等腰直角三角形MNP区域内存在垂直于坐标平面向外的匀强磁场,y<0的区域内存在着沿y轴正方向的匀强电场
.一质量为m、电荷量为q的带电粒子从电场中Q点以速度v0水平向右射出,经坐标原点O射入第Ⅰ象限.已知粒子在第Ⅲ象限运动的水平方向位移为竖直方向位移的2倍,且恰好不从PN边射出磁场.已知MN平行于x轴,N点的坐标为(2h,2h),不计粒子的重力,求:
![](https://img.xkw.com/dksih/QBM/2019/12/11/2352713616891904/2354086114385921/STEM/6e129a68-8f3c-4081-9afa-d5bf412d7451.png?resizew=224)
⑴入射点Q的坐标;
⑵磁感应强度的大小B;
⑶粒子第三次经过x轴的位置坐标.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/113db10be77011439db4dae8f54c1074.png)
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⑴入射点Q的坐标;
⑵磁感应强度的大小B;
⑶粒子第三次经过x轴的位置坐标.
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