问题 多选题

下列情况中的加点的物体,哪些可以看作质点?(  )

A.研究从北京开往上海的一列火车的运行速度

B.用GPS确定远洋海轮在大海中的位置

C.体育教练员研究百米跑运动员的起跑动作

D.研究地球上昼夜交替原因

答案

A、火车从北京到上海的距离比火车的长度大的多,此时火车的长度可以忽略,火车可以看成质点,故A正确.

B、用GPS确定远洋海轮在大海中的位置时,卫星到海面的距离远大于船的长度,故此时的船看作质点.故B正确.

C、研究百米跑运动员的起跑动作时,教练要观察他的动作是否规范,不能把他看作质点.故C错误.

D、地球绕着地轴不停地旋转叫地球的自转,地球自转产生的现象是昼夜交替和时间差异,此时的地球不可以看成是质点,故D错误.

故选AB.

阅读理解

The World's Largest Insect .This giant insect can be used as a toy.

A child ties one end of a string to a stick and the other end around the "neck" of an insect. Holding the stick, the child lets the insect go. With a loud whirring sound, the insect takes off, pulling the string in a large curve over the child's head. The child laughs as the stick jumps around. The child is African, and the toy is the African Goliath beetle, the largest insect in the world.

The Goliath is a true insect because it has six legs and a body that is divided into three parts. Like all beetles, it has two pairs of wings. The front pair are thick and stiff and protect the back pair, which are soft. It is these soft back wings that make the beetle fly forward. They also cause the loud whirring sound the beetle makes when it flies. To steer, the beetle twists and turns its legs the same way you steer a bike by turning its front wheel.

African children often use the Goliath beetle as a toy. Although it is over 15 centimeters long, it is quite harmless.

小题1: The African Goliath beetle is _______. 

A.the world's largest insect

B.a toy used in many parts of the world

C.the only insect found in Africa

D.the world's smallest insect小题2:What do African children often use the Goliath beetle as?

A.a tool.

B.a toy.

C.harmfull insects.

D.Good animals.小题3:We know the Goliath beetle is a true insect because it _______. 

A.makes a whirring sound when it flies

B.has both soft and hard wings

C.has six legs and a body with three parts

D.can fly小题4:When flying, the Goliath steers by_______. 

A.turning its soft back wings

B.twisting and turning its hard front wings

C.twisting and turning its legs

D.twisting and turning its whole body

单项选择题