题目

某质点在平直轨道上运动的v-t图像如图所示，则下说法正确的是（ ）A.0~1s内与2~3s内质点的速度方向相反B.0~1s内与2~3s内质点的加速度相同C.0~2s内与0~4s内质点的位移相同D.0~2s内与0~4s内质点的路程相同 答案：【答案】C【解析】A．0~1s内与2~3s内质点的速度都是正值，都向正方向运动，A错误；B．0~1s内质点的加速度向正方向，2~3s内质点的加速度向负方向，B错误；C．0~2s内与0~4s内质点的位移相同，都等于3m，C正确；D．0~2s内的路程小，0~4s内质点的路程大，D错误。故选C。 Lightning is one of the most beautiful natural phenomena(现象).It is also one of the most deadly phenomena. A bolt of lightning is six times hotter than the surface(表面)of the Sun and gives out 30，000 amps of electricity(电).It can travel at 100, 000 kilometres per hour and has the ability to hit an object up to 40 kilometres away. About 1,000 people around the world are killed by lightning every day.Only about ten percent of people struck by lightning will actually die, but the others are actually very badly injured, with burns, broken bones, blindness, deafness, paralysis, or memory loss. However, when the electricity passes through their brain, it can occasionally have unusual and even positive effects. Some blind people have got their sight back after being struck by lightning. One woman said a psychological(心理的)test showed her intelligence (智力)had greatly improved, and one man said he could no longer feel cold at all and could go out in temperature below freezing in just a T-shirt!So what should you do to stay safe in a thunderstorm? The most important rule is to stay inside, but do not go near phones, electrical appliances, plumbing, or water. If you are stuck(困住)outside, do not take shelter under a tree. Instead, roll yourself up into a ball on the ground as small as possible. And do mot think it has to be raining in order for lightning to strike.Strangely, lightning seems to prefer some people to others. If you are a man, you are six times more likely to be struck by lightning than a woman!1.What does the phrase " positive effects”in Paragraph Two possibly mean?A.something good B.something badC.something strange D.something useless2.In order to stay safe in a thunderstorm, you should not .A.stay inside B.roll up into a ballC.take shelter under a tree D.stay away from water3.Which of the following is TRUE according to the article?A.Lightning is a beautiful but dangerous phenomenon.B.Most people struck by lightning will actually die.C.Lightning can travel at 10,000 kilometers per hour.D.A woman is more likely to be struck by lightning than a man.4.The writer uses the examples of a man and a woman in Paragraph Two to .A.show lightning is very dangerous to human beingsB.make the readers want to know more about lightningC.help people know lightning will surely improve their intelligenceD.prove something interesting may happen because of lightning5.You may read this passage in .A.a story book B.a science magazineC.a tour guide book D.an advertisement