Hard图示长为L的杆AB沿墙壁和地面移动，已知A点以速度vA匀速运动，则夹角θ为45°时，B点的加速度大小为（）。
A: 2.828vA^2/L
B: vA^2/L
C: 0
D: 1.414vA^2/L
A: 2.828vA^2/L
B: vA^2/L
C: 0
D: 1.414vA^2/L
举一反三
- 图示杆AB沿墙壁和地面移动，已知A点以速度vA匀速运动，则夹角θ为45°时，B点的速度大小为（）。[img=450x365]17869457ac671e4.png[/img] A: 1.414vA B: 0 C: 2vA D: vA
- 如图所示，电路中A点的电位VA为（）。<img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202009/4115d0188a984061a263007ff7ba743a.png" > A: ﹣10V B: ﹣6V C: ﹣4V D: 0V
- 一根直径为d=16mm、长为L=3m的圆截面杆，承受轴向拉力P=30kN，其伸长为ΔL=2.2mm，则杆材料的弹性模量E为（ ）。 A: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202103/a181a74d8aad41cf86ae169737f9466b.png" /> B: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202103/37d2cf0c95714c99995e13d9e87673c8.png" /> C: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202103/53f9241fce8d4b28868f01f4a0a70116.png" /> D: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202103/d57a95bb7d944dfc93a645612f3380aa.png" />
- 下列结论错误的是（） A: 如果函数<img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202009/18a10ebd75f54d9ba2de6c77fb99c56d.png">在点<img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202009/3e7d8d0d9aba463faf8ba22335557789.png">处连续，则<img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202009/18a10ebd75f54d9ba2de6c77fb99c56d.png">在点<img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202009/3e7d8d0d9aba463faf8ba22335557789.png">处可导 B: 如果函数<img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202009/18a10ebd75f54d9ba2de6c77fb99c56d.png">在点<img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202009/3e7d8d0d9aba463faf8ba22335557789.png">处不连续，则<img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202009/18a10ebd75f54d9ba2de6c77fb99c56d.png">在点<img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202009/3e7d8d0d9aba463faf8ba22335557789.png">处不可导 C: 如果函数<img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202009/18a10ebd75f54d9ba2de6c77fb99c56d.png">在点<img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202009/3e7d8d0d9aba463faf8ba22335557789.png">处可导，则<img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202009/18a10ebd75f54d9ba2de6c77fb99c56d.png">在点<img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202009/3e7d8d0d9aba463faf8ba22335557789.png">处连续 D: 如果函数<img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202009/18a10ebd75f54d9ba2de6c77fb99c56d.png">在点<img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202009/3e7d8d0d9aba463faf8ba22335557789.png">处不可导，则<img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202009/18a10ebd75f54d9ba2de6c77fb99c56d.png">在点<img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202009/3e7d8d0d9aba463faf8ba22335557789.png">处也可能连续
- 通过点<img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202009/a13927df1bf542dfa036a32b10364f69.png" />的拉格朗日插值基函数<img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202009/65695a42c7a14b649b6aa4fb68f7e499.png" />满足( ) A: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202009/99af333f3e934ef6a75022ee1e728b53.png" />＝1，<img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202009/7769611ac5cd4c93975be7c41a49ae71.png" /> B: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202009/99af333f3e934ef6a75022ee1e728b53.png" />＝1，<img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202009/7769611ac5cd4c93975be7c41a49ae71.png" /> C: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202009/99af333f3e934ef6a75022ee1e728b53.png" />＝0，<img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202009/7769611ac5cd4c93975be7c41a49ae71.png" /> D: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202009/99af333f3e934ef6a75022ee1e728b53.png" />=0，<img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202009/f80e8e400f3f4916bcaf6b5fde757f16.png" />