搜题请搜索小程序“爱下问搜题”
问题 问答题

地球周围存在着吃磁场，由太空射来的带电粒子在此磁场中的运动称为磁漂移．以下是描述一种假设的磁漂移运动．在某真空区域有一质量为m电量为q的粒子（重力不计），在x=0，y=0处沿y方向以速度v0运动，空间存在垂直纸面的匀强磁场，在y＞0的区域中，磁感应强度为B1，在y＜0的区域中，磁感应强度为B2，且B1与B2的方向相同，B1＜B2，粒子在磁场区域内沿x正方向作磁漂移运动，如图所示．

（1）磁感应强度B1与B2的方向如何？

（2）把粒子出发点x=0处作为第0次通过x轴，求第2次过x轴时粒子沿x轴漂移的距离．

（3）从第0次通过x轴，到第2次过x轴时粒子沿x轴方向漂移的平均速度．

答案

（1）根据左手定则，粒子受到的洛伦兹力向右，所以磁感应强度B1与B2垂直纸面向外．

（2）设带电粒子在B1和B2中运动的半径分别为r1和r2，周期分别为T1和T2，由公式qvB=m

v2
r

得r1=

mv0
qB1
；  r2=
mv0
qB2

粒子第2次过x轴时粒子沿x轴的位移为x=2(r1-r2)=2(

mv0
qB1
-
mv0
qB2
)

（3）粒子做圆周运动的周期T1=

2πm
qB1
；T2=
2πm
qB2

从第0次通过x轴，到第2次过x轴运动的时间t=

1
2
(T1+T2)

由平均速度v=

x
t

解得：v=

2v0(B2-B1)
π(B1+B2)

答：（1）磁感应强度B1与B2垂直纸面向外；

（2）第2次过x轴时粒子沿x轴漂移的距离x=2(

mv0
qB1
-
mv0
qB2
)．

（3）从第0次通过x轴，到第2次过x轴时粒子沿x轴方向漂移的平均速度v=

2v0(B2-B1)
π(B1+B2)
．

问答题 简答题

什么是无害化处理？
查看答案
阅读理解
任务型读写。
     阅读下面短文,根据所读内容在表格中的空白处填入恰当的单词.
注意：每个空格只填一个单词。

     Dennis Hopper, who was described as "Easy Rider's" biker Billy and "Blue Velvet's", died of cancer
Saturday morning at his home in Venice, California. He was 74.
     Hopper, who was diagnosed with cancer last October, was surrounded by his children and wife when
he died. The American film star made his last public appearance on March 26, 2010, when his star was
addressed on Hollywood's Walk of Fame.
     Dennis Hopper was born in Dodge City, Kansas, on May 17, 1936. He grew up in San Diego,
California, and got an early reputation for stage work. Making his way to Hollywood while still in his teens,
he quickly earned roles in several films and TV shows, including "Rebel Without a Cause" (1955), in which
he met James Dean, who became a friend and life-long model.
     Hopper maintained a somewhat not smooth career through the mid-60s. But it was 1967s. "The Trip",
directed by "King of the B's" Roger Corman, that made the actor popular with audience and two of his
"Easy Rider" colleagues, actor Peter Fonda and "The Trip" writer Jack Nicholson.
     In early 1968, Hopper led the group through his own low-budget film, a biker road movie about two
riders who travel from Los Angeles to New Orleans. "Easy Rider" was finally released in the summer of
1969, and was very popular after 1967's "Bonnie and Clyde" and "The Graduate", the breakthrough that
set free the baby boomer generation on Hollywood.
     The film, made on the fly by Hopper and co-star Fonda for less than $ 500,000, became one of the
most popular movies of its time.
     Among his recent roles were a villain (反面人物) in the TV series "24" and an officer in the short-lived
TV show "E-Ring". He was starring in the TV version of the Oscar-winning film "Crash" at his death,
playing a record producer. He was named a chevalier (功勋人物) of France's Order of Arts and Letters
in 2008.
TitleEasy Rider's actor (1)_____
The(2)_____ of his death●He died of cancer．
Age●He was 74. 
The (3)_____ of birth●He was born on May 17, 1936. 
The (4)_____ of his career●He became (5) _____ in his teens.
●He began to play roles in many films.
●His career was not (6) ____ in the mid-60s.
●1967's "The Trip", (7) _______ his popularity again.
●He made a major (8) _______ in his career because of "Easy Rider".
●He played a record (9) ______ in the TV version "Crash"
(10)_______●He was named a chevalier of France's Order of Arts and letters in 2008．
查看答案