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问题 选择题

如图所示，三维坐标系O-xOy的z轴方向竖直向上，所在空间存在y轴正方向的匀强电场，一质量为m、电荷量为+q的小球从z轴上的A点以速度v0水平抛出，A点坐标为（0，0，l），重力加速度为g，场强E=

mg
q
．下列说法中不正确的是（　　）

A．小球做非匀变速曲线运动

B．小球运动的轨迹所在的平面与xOy平面的夹角为45°

C．小球的轨迹与xOy平面交点的坐标为（v0

2l
g
，l，0）

D．小球到达xOy平面时的速度大小为

v20+4gl

答案

A、小球在水平抛出后受力情况为：沿Z轴负方向的重力mg，沿y正方向的电场力qE=q×

mg
q
=mg，

故小球所受的合力大小为F=

2
mg，

根据F=ma可得物体的加速度a=

2
mg
m
=
2
g，加速度a方向为y轴负方向偏z轴负方向45°，

故加速度方向与初速度方向不在同一条直线上，故物体做匀变速曲线运动．

故A错误．

B、由于小球的初速度v0与加速度a所在的平面与xoy平面的夹角为45°，

故小球运动的轨迹所在的平面与xOy平面的夹角为45°，故B正确．

C、沿z轴负方向的位移为L在到达xoy平面前小球沿加速度方向通过的位移为

2
L，

故其沿y轴方向的位移y=

2
Lcos45°=L，

设小球到达xOy平面的时间t，

故有L=

1
2
gt2，

所以t=

2L
g
，

沿x轴方向的位移x=v0t=v0

2L
g
，

故小球的轨迹与xOy平面交点的坐标为（v0

2l
g
，l，0），

故C正确．

D、小球沿加速度方向的速度v1=

2ax
=
2
2
g×
2
L
=2
gL

小球到达xOy平面时的速度大小为v=

v02+v12
=
v02+4gL
，

故D正确．

本题选不正确的，故选A．

选择题

As we all know, it is not important where you come from, but it really ________ where you are going.

A．cares

B．works

C．matters

D．functions
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阅读理解
阅读理解。
     警方近期正在缉拿一系列案件的嫌疑人员.阅读下面有关警方通报查找人员的信息(A、B、C、D、E和F)，根据案件及人物的描述,选出嫌疑人员，选项中有一项是多余的。
1. A valuable dog was taken while being walked by its owner in City Park yesterday afternoon. Police
wish to talk to a man seen nearby at the time, described by witnesses as short and fat with short light hair
and clear glasses.
2. Yesterday morning at 9.30a.m. a man armed with a gun entered the National Bank and demanded
money from the staff, before fleeing when confronted by bank security staff. Security cameras show the
man as being short and thin with shoulder length blonde hair.
3. A tall, strong built man with blonde hair, a thick black moustache and wearing dark glasses knocked
a woman to the ground and stole her purse on Main Street last Saturday afternoon. If you see this man,
do not approach as he is considered extremely dangerous.
4. At the football match between Manchester United and Liverpool, several people had their wallets
stolen while waiting in line to buy food. The victims did not see or notice the thief but bystanders describe
him as very tall and thin, clean shaven with short light hair.
5. A car was stolen from the supermarket carpark on Friday, June 23 this year by a man described as
very young, 1.7 metres tall with thin dark hair and carrying a blue backpack. A reward of $500 is offered
for the car's recovery.

A
Name: Ziggy Nizott
Height: 1.82 m
Weight: 90kg
Age: 35
Details: Long history of violent crime
including robbery, assault and car theft.




B
Name: Dennis Tsokas
Height: 1.95 m
Weight: 70 kg
Age: 28
Details: Well known to local police having been
arrested several times for pick-pocketing.



C.  
Name: Michael Clarke
Height: 1.7 m
Weight: 65 kg
Age: 20
Details: Arrested as a youth for
car theft and the selling of stolen goods.




D. 
 Name: Mark Hughes
Height: 1.6 m
Weight: 60kg
Age: 29
Details: Is wanted by police for several armed
robbery of grocery stores, banksand post offices.


E.  
Name: Herb Elliot
Height: 1.6 m
Weight: 90kg
Age: 22
Details: Recently released from prison                  
where he served 2 years   for selling stolen goods


F.  
Name: William Daniels
Height: 1.6 m
Weight: 90kg
Age: 32
Details: Arrested 4 times for the
selling of  drugs and car theft.
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