涡旋电流的存在条件如果一个单位点电荷在匀强磁场中 磁场强度均匀变化 点电荷受力吗?如果一个闭合环形轨道内只存在一种电性的

旋窝震荡太强烈了.很可能会损坏质粒,同时如果染色质结构被破坏,可能会污染到质粒样本

解题思路：两个物体均只受重力和支持力，靠重力和支持力的合力提供圆周运动的向心力，根据F合=ma=mv2r=mrω2=mr4π2T2，比较线速度、角速度、向心加速度、周期的大小．

对任一物体受力分析，物体受到重力和支持力，它们的合力提供向心力，如图

根据牛顿第二定律，有：F_向=mgtanθ=m
v2
r=mrω²=ma=mr
4π2
T2，则得：
A、线速度v=
grtanθ，由于A球的转动半径较大，A线速度较大．故A正确；
B、角速度ω=

gtanθ
r，由于A球的转动半径较大，A的角速度较小，故B错误；
C、向心加速度 a=gtanθ，与r无关，则两个物体的向心加速度大小相等．故C错误．
D、周期T=2π

r
gtanθ，则得A的周期必定大于B的周期，故D正确．
故选：AD．

点评：
本题考点： 线速度、角速度和周期、转速．

考点点评： 本题关键是建立模型，对物体受力分析，知道小球做圆周运动向心力的来源，运用牛顿第二定律进行求解．

小于

解题思路：在流体中流速越大的位置压强越小，流速越小的位置压强越大．

高速旋转的气流．内部气流高速旋转，内部气体流速大，压强小，外部气体流速小，压强大．
故答案为：小于．

点评：
本题考点： 流体压强与流速关系的探究实验．

考点点评： 此题考查的是流体压强在生活中的应用，这就要求我们平时要多观察生活．

龙卷风是一种强烈的、小范围的空气涡旋,是在极不稳定天气下由空气强烈对流运动而产生的,由雷暴云底伸展至地面的漏斗状云(龙卷)产生的强烈的旋风.
Tornado is a small range of fierce vortex of air which causes by the violent convection movement of air in extremely instable weather.
It’s a violent cyclone produced by clouds shaped like filler which spreads from the bottom of thunderstorm cloud to the ground.
龙卷的袭击突然而猛烈,产生的风是地面上最强的.在美国,龙卷风每年造成的死亡人数仅次于雷电.它对建筑的破坏也相当严重,经常是毁灭性的.
在强烈龙卷风的袭击下,房子屋顶会像滑翔翼般飞起来.一旦屋顶被卷走后,房子的其他部分也会跟着崩解.因此,建筑房屋时,如果能加强房顶的稳固性,将有助于防止龙卷风过境时造成巨大损失
Tornado attacks abruptly and fiercely,bringing in the strongest wind on the ground.In American,deaths caused by tornado each year are merely less than those by thunder.Moreover,it creates severe damages to the buildings,constantly destructive.
Roof of building will rise up like the wings of gliders under the intense attack of tornado.And once roof is whirled away,the other parts of building will break down as well.Consequently,strengthening the fixedness of the roof will help to avoid the huge breakage when tornado lands on.

（1）夏季最多，冬季最少（2分）；沿海多，内陆少（东南多西北少；东多西少；大型水体多丘陵山地少）（2分）；沿海地区（东南地区）地势平坦，河网密布，加之夏季的高温闷热天气，龙卷风多发。（2分）
（2）危害：强风使庄稼果木瞬间被毁，交通中断，房屋倒塌，人畜生命遭受损失（3分）。防御措施：加强对龙卷风的跟踪监测、预报；加固房屋等基础设施；大力加强宣传，积极参与防灾减灾工作等（6分）


（1）由龙卷风的概念和江苏省龙卷风发生次数（1951—2007年累计）分布图可以判断，江苏省龙卷风灾害的时空分布特点：夏季最多，冬季最少；沿海多，内陆少（东南多西北少；东多西少；大型水体多丘陵山地少）。原因：沿海地区（东南地区）地势平坦，河网密布，加之夏季的高温闷热天气，龙卷风多发。
（2）龙卷风的主要危害：强风使庄稼果木瞬间被毁，交通中断，房屋倒塌，人畜生命遭受损失。防御措施：加强对龙卷风的跟踪监测、预报；加固房屋等基础设施；大力加强宣传，积极参与防灾减灾工作等。

The tornado is a 涡旋 ：dragon air around the shaft to rotate rapidly,by a tornado center pressure was reduced to attract,dozens of a thin layer of air currents from all sides,by inhalation 涡旋 bottom.and then into the vortex of 轴心,the strong wind always cyclones,the centre of pressure around 10% lower than the pressure.
The atmosphere of instability have a strong rising air currents,the current in the flow of traffic,it was further strengthened
In a vertical,horizontal with the speed and direction are never get wind of interaction,rising air currents in the troposphere central began to revolve,forming scale necessitated
With the scale necessitated to the development and progress,itself became fine and strengthened.meanwhile,a small area of increased support to that of the dragon born in the form,cyclones necessitated the same process and the formation of a tornado core
A tornado's whirling core and cyclones in,it was strong enough to make a tornado to the ground.when development reached the surface pressure,the ground with a sharp rise to form strom

作者用描写和比喻的手法
先是形容了主人公她的体态和舞姿,之后修饰了眼睛.表现出了她的与众不同的美艳,刻画出了她在作者心目中的美好形象.具体的联系文章再写点就成

Typhoon is actually strong tropical cyclone.Tropical cyclones occur in tropical oceans on the strong weather system as it flows in the river in advance of the vortex,around the side of the center of their rapid rotation,while moving forward with the surrounding atmosphere.In the Northern Hemisphere tropical cyclones in the air flow around the center were anti-clockwise rotation,the opposite is true in the Southern Hemisphere.The more close to the center of tropical cyclones,the lower the pressure,the greater the wind.However,the development of strong tropical cyclones,such as typhoons,its center was calm but clear zone,that is,the typhoon eye.
In the tropical oceans on the occurrence of tropical cyclones,the intensity of their differences.When a tropical cyclone near the center of the largest wind power is less than 8 hours as the tropical low pressure,8 and 9 as the tropical storm's winds,10 and 11 the wind was stronger tropical storm,the only center in the vicinity of the largest wind power reached 12 tropical cyclones It is called a typhoon.
Tropical cyclone formation and development of the huge energy needs,so it was formed in the high-temperature,high humidity and other weather conditions suitable for the tropical sea surface.According to statistics,with the exception of the South Atlantic,the world's tropical oceans have on tropical cyclone formation

由于地球自西向东自转,地球上的运动物体均受到科里奥利力的作用.科里奥利力的方向总是和物体运动的速度方向垂直并指向运动轨迹的右边（即速度矢量与地球自转角速度矢量叉乘的方向）.澡盆里的水也是因为这个原因作逆时针旋转的.当然,如果在南半球,水则是作顺时针旋转.