问题 问答题

______叫匀速直线运动; ______叫变速运动.把变速运动当作简单的匀速直线运动来处理,即把物体通过的路程和通过这段路程所需时间的比值,称为物体在这段路程或这段时间内的 ______,它只能粗略的描述物体运动的快慢.

答案

速度保持不变的直线运动叫匀速直线运动.

速度改变的运动叫变速运动.

平均速度是物体通过的路程和通过这段路程所需时间的比值.

故答案为:速度保持不变的直线运动,速度改变的运动,平均速度.

阅读理解

阅读短文,选择正确答案。

    Elephants are interesting animals with large ears, a long trunk, and short legs. They use their legs to stand and

walk. Unlike (不像) lions and tigers, an elephant cannot use its legs to jump or run fast. But elephants do have

something that most animals do not have — a trunk!

    It is difficult for an elephant to bend (弯曲) down to reach food on the ground because of its short, fat legs.

That is why an elephant has a trunk. It uses its trunk to reach food it needs. Without its trunk, an elephant would

be helpless.

    An elephant uses its trunk as a monkey might use its arms and hands. The elephant can scratch (抓) an itch

(痒), pick up a small peanut (坚果) or a piece of popcorn (爆米花), and touch objects with its trunk. An

elephant's trunk can even wrap (裹) around a tree and pull it out of the ground. An elephant's trunk also helps it

drink water. An elephant can drink as much as 50 gallons (加仑) of water into its trunk. Then the elephant

squirts (喷出) the water into its mouth and down its throat (喉咙). An elephant's trunk is very useful!

1. In paragraph 2, helpless means _______. [ ]

A. without help

B. with help

C. trying to help

D. full of help

2. What is one way that the elephant's trunk is like a monkey's hands? [ ]

A. Both have fingers (手指).

B. Both squirt water.

C. Both can hold food.

D. Both have fingernails (指甲).

3. This story mostly tells the reader that elephants ________. [ ]

A. use their short legs to find food

B. are stronger than most animals

C. drink water once a day

D. would be helpless without a trunk

单项选择题