一块梯形菜地上底是20米,下底是30米,高是28米,共收白菜4200千克,平均每

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问题:

一块梯形菜地上底是20米,下底是30米,高是28米,共收白菜4200千克,平均每平方米收白菜多少千克?

考点:梯形的面积
题型:解答题

(1)在《测定匀变速直线运动的加速度》实验中,纸带的E端与小车连接,得到如图所示的一条纸带.已知打点计时器打点的时间间隔为0.02s,纸带上的各个点均为计数点(相邻两个计数点之间还有四个点图中未画出).用毫米刻度尺测量从某点O(O点图中未画出)到 A、B、C、D、E各点的距离依次是(单位为cm):3.00、3.30、3.80、4.50、5.40.

则实验中小车的加速度大小是______m/s2,加速度方向是从C点指向______(填B或D)点.打点计时器打下C点时小车的速度大小为______m/s.

(2)某同学用如图所示的装置测定重力加速度,

①电火花计时器的工作电压为______,频率为______.

②打出的纸带如图所示,实验时纸带的______端应和重物相连接.(选填“甲”或“乙”)

③由纸带所示数据可算出实验时的加速度为______m/s2

④当地的重力加速度数值为9.8m/s2,请列出测量值与当地重力加速度的值有差异的一个原因:______.

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长江被称为“黄金水道”的主要原因是(  )

A.水力资源丰富

B.流域内多矿产

C.年径流量大

D.航运价值高

题型:解答题

Parents are often amazed at how fast their child grows and develops. New research has determined that the ability to quantify may develop much sooner than most parents realize.

Kristy Vanmarle, professor of the University of Missouri, has determined that contrary to what previous studies have shown, infants(婴儿)are able to quantify substances(物质)—like sand or water—as early as 10 months. As long as the difference between the two substances is large enough, infants will choose the larger amount, especially when it comes to food.

With the assistance of her team researchers, Vanmarle tested the quantifying skills of babies by presenting them with two cups: one containing a small amount of food, and one containing a larger amount. Consistently, the babies chose the larger amount.

“Several studies throughout the last 15 years have shown that infants are very good at telling how many objects they see; however, infants don’t seem to count things like water or sand,” Vanmarle said. “What we’re saying is that they can quantify substances; it’s just much harder. The infants can see how much food goes into each cup and compare that in their memories. They decide which amount is larger, and they almost always select the larger one.”

“This information further refutes(驳斥)the long-held idea that babies know nothing of the world,” Vanmarle said.

“Since psychologists have begun studying infants with sensitive measures, we’ve discovered a lot of early abilities. I think for parents, it should be exciting to know that there’s somebody in there that has some fundamental and basic knowledge of the world, and that knowledge is guiding their development,” Vanmarle said.

In the future, Vanmarle says this kind of study could be linked to a child’s progress in math-related skills, although programs marketed to increase those abilities, such as “Baby Einstein,” still have mixed reviews when it comes to academic study.

小题1: The quantifying ability refers to the ability to     .

A.choose between different substances

B.describe the quantity of something

C.get much knowledge of the world

D.obtain math-related skills小题2: What is mainly talked about in Paragraph 4?

A.The process of doing research.

B.The final choice of infants.

C.The scientific findings.

D.The observation of infants’ behavior.小题3: Babies choose the larger amount of food     .

A.through their natural abilities

B.with the help of parents

C.on personal preference

D.by saying numbers小题4:We can learn from the text that     .

A.some parents don’t care about their kids

B.scholars disagree on baby-training programs

C.little research has been done on infants

D.people used to think the world is known to babies小题5:What’s the best title of the text?

A.Unique Quantifying Methods

B.Amazing Baby-training Ideas

C.Early Human Abilities

D.Breakthrough in Baby Studies

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本课程培训需要提交的作品有()。

A、1个。

B、2个。

C、3个。

D、4个。

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