试题与答案

小丽同学在探究“滑动摩擦力的大小跟哪些因素有关”的过程中,作了以下猜想: A.可能

题型:问答题

题目:

小丽同学在探究“滑动摩擦力的大小跟哪些因素有关”的过程中,作了以下猜想:A.可能与接触面的粗糙程度有关;B.可能与接触面间的压力大小有关; C.可能与产生摩擦力的两物体间接触面积的大小有关.为了检验上述有关猜想是否正确,她设计如图所示的三个实验步骤:

(1)实验中,弹簧测力计显示的读数是拉力F的大小,根据______条件可知F等于摩擦力f;实验中关键是要保证木块做______运动.

(2)比较甲、乙两次实验可以得到:滑动摩擦力的大小与______有关.

要想验证猜想A可以比较实验______和实验______.

(3)为了检验“猜想C”是否正确,可在上述实验甲的基础上在增加一个步骤,写出你所设计的这一实验步骤.步骤:______.

答案:

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题型:阅读理解

An African-American man named John Henry was the hero of former slaves and the people who built the railroads in the US in the 19th century.

John Henry was born a slave. He was known for his strength. Many people say he represents the spirit of growth in America during that period.

John Henry grew up in a world that did not let children stay children for long. Before he was six years old, he was carrying stones for workers building a nearby railroad. By the time John Henry was a young man, he was one of the best railroad workers in the country.

John Henry was asked to lead workers on a hard project, creating a tunnel through a mountain. The project required about 1,000 laborers and lasted three years. Hundreds of men became sick as a result of the hot weather and tiredness. John Henry was the strongest and fastest man. Concerned his friends might lose their jobs, he picked up their hammers and began doing their work. He worked day and night, rarely stopping to have a rest.

One day, a salesman came to the work area with a new drilling machine powered by steam. He said it could drill holes faster than twelve men working together.

John Henry looked at the machine and saw images of the future. He saw machines taking the place of America’s best laborers. He saw himself and his friends unemployed and sanding by a road, asking for food. He decided he would never let the machine take their jobs. Therefore, a competition between a man and a machine began .At first, the steam-powered drill worked twice faster. Then, John Henry started working with a hammer in each hand. He worked faster and faster. People cheered when the machine broke down and was pulled away. But they were sad to find John Henry fall to the ground, with blood spilling all around, and still holding a hammer in one of his hands.“I beat them,”he said. Then he took his last breath.

小题1:What does the underlined part in Paragraph 3 most probably mean?

A.Many children in those days starved to death.

B.Children at that time grew much faster.

C.Children in those days had to work like adults.

D.Children at that time couldn’t stay together.小题2:Why did hundreds of workers become sick?

A.Because they had to work long hours.

B.Because the weather was hot and they were tired.

C.Because the project was too hard.

D.Because they didn’t have time to eat.小题3:John Henry helped do his friends’ work     .

A.because he was the strongest and fastest man

B.for fear that his friends would lose their jobs

C.so that they could regain their strength

D.in order be the hero of the railroad workers小题4:Which of the following best describes John Henry?

A.Kind and determined.

B.Cautious and considerate.

C.Brave and strict.

D.Hardworking and stubborn.

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题型:问答题

我国北方常遭遇严重的沙尘暴天气.所谓沙尘暴可以简化为如下情景:快速向上刮起的大风将大量沙尘颗粒扬起后悬浮在空中(不动),这时风对沙尘的作用力与沙尘的重力平衡,其作用力大小可近似表达为,其中ρ为空气密度,S为沙尘颗粒的横截面积,v为风速.如果沙粒的密度ρ为3×103kg/m3,沙粒半径r为2.5×10-4m,地面的空气密度ρ0为1.25 kg/m3,那么要形成沙尘暴现象,地面的风速至少为_________m/s.假设空气密度ρ随地面高度h的变化关系如图所示,那么当地面风速为8m/s时,当地沙尘暴的最大高度为_________m.(g取10N/kg,沙粒可近似看成球体,且体积)

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题型:问答题

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若在结婚前甲对乙谎称其父亲为亿万富翁,结果其父只是一个普通农民,乙在知晓此情况后是否可以行使撤销权

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