如图所示,将带电粒子从电场中的A点无初速地释放,不计重力,下列说法正确的是( )

题型:多选题

问题:

如图所示,将带电粒子从电场中的A点无初速地释放,不计重力,下列说法正确的是(  )

A.带电粒子在电场中一定做加速直线运动

B.带电粒子的电势能一定逐渐减少

C.带电粒子一定向电势低的方向运动

D.带电粒子的加速度一定越来越小

考点:牛顿第二定律电场线电势能电势
题型:多选题
已知二次函数y=-
1
2
(x-
3
2
)2+
25
8
的图象在坐标原点为O的直角坐标系中,
(1)设这个二次函数的图象与x轴的交点是A、B(B在点A右边),与y轴的交点是C,求A、B、C的坐标;
(2)求证:△OAC△OCB.
题型:多选题

脾约证的脉象是()

A.脉滑而疾

B.脉沉迟

C.趺阳脉浮而涩

D.脉浮大

E.脉微涩

题型:多选题

Can storms in Africa cause asthma(哮喘) in the Caribbean(加勒比)? Islanders point to the desert insects that land on beaches after a 5,000-kilometer flight across the Atlantic. If they can use winds to get from one continent to another, so can clouds of dust that carry disease.

Scientists think that as Africa becomes drier, dust from expanding deserts is being blown away into Caribbean islands. A study in Barbados shows that asthma has increased 17 times since Africa’s drought(干旱) began in 1973.

Other forms of life are suffering, too. Among them are the Caribbean’s famous coral reefs( 珊瑚礁), which began dying in large numbers in the 1900s. Eugene Shinn of the U.S. Geiological Sudrvey(USGS) in Florida went to the virgin Islands to study the reefs. The tests he and his colleagues carried out showed that the coral was dying of disease caused by Africa microbes(微生物) from across the ocean.

William Sprigg of the University of Arizona is studying the problem as part of a major UN project. He says that dust is causing problems in the U.S., too.

“We are just beginning to collect the evidence of airborne(空气传播的) dust influences on human health,” he told The Washington Post.

小题1:Which of the following can be the best title for this passage?

A.Dangerous Dust

B.Dangerous Disease

C.Changing Weather

D.Developing Technology小题2: Where does the dust talked about in this passage come from?

A.America.

B.Africa.

C.The Atlantic.

D.The Pacific.小题3: The increase of asthma in the Caribean is probably related to _____ according to scientists.

A.desert insects

B.strong winds

C.airborne dust

D.dry weather小题4:Which of the following is NOT true about the Caribbean coral reefs?

A.They are in Florida.

B.They used to be very beautiful.

C.They began dying in the past decades.

D.The African microbes have bad effect on them.小题5: Which of the following is TRUE about William Sprigg?

A.He is a member of UN.

B.He thinks African dust also affects the US.

C.He has collected enough evidence about dust influences.

D.He is a reporter from The Washington Post.

题型:多选题

寄存人向保管人交付保管物的,保管人应当给付______。

A.担保金
B.保管凭证
C.抵押金
D.信用保证金

题型:多选题

基金经理的市场时机选择能力会导致基金组合的绩效和市场组合之间存在( )。

A.(A) 线性关系

B.(B) 非线性关系

C.(C) 不确定关系

D.(D) 反向变动关系

更多题库