问题 多选题

下列说法正确的是(  )

A.拔河比赛时,胜方拉对方的力大于败方拉对方的力

B.马能拉车前进是因为马对车的拉力大于车对马的拉力

C.太阳对地球的吸引力与地球对太阳的吸引力大小一定相等

D.用铁锤钉钉子,锤对钉的打击力与钉对锤的作用力大小一定相等

答案

A、拔河比赛时,绳子(轻绳m=0)受到两个拉力,根据牛顿第二定律,有:F1-F2=ma=0;由于人拉绳子的力和绳子拉人的力是相互作用力,相等;故胜方拉对方的力等于败方拉对方的力;故A错误;

B、马能拉车前进是因为马对车的拉力大于地面对车的阻力,故B错误;

C、太阳对地球的吸引力与地球对太阳的吸引力是相互作用力,故大小一定相等,故C正确;

D、用铁锤钉钉子,锤对钉的打击力与钉对锤的作用力是相互作用力,大小一定相等,故D正确;

故选CD.

单项选择题
阅读理解

阅读理解。

     Hi, boys and girls! Do you know how to be a healthy kid? Here are some rules you should follow.

     First, eat different foods, especially fruit and vegetables. You may have a favorite food, but you'd

better eat something different; if you eat different foods, you will probably get more nutrients your body

needs.

     Second, drink water and milk as often as possible. When you're really thirsty, cold water is the NO.1

choice. Milk is a great drink that can give you more calcium your body needs to grow strong bones.

     Third, listen to your body. How do you feel when you are full? When you are eating, notice how your

body feels and when your stomach feels comfortably full. Eating too much will not make you feel

comfortable and make you fat.

     Fourth, limit screen time. Screen time is the time you watch TV, DVDs and videos, or using

computers. It is good to take more exercise such as basketball, bike riding and swimming. You can't

watch TV for more than two hours a day.

     Fifth, be active.One thing you'd like to do as a kid is to find out which activity you like best. Find ways

to be active every day.

     Follow these rules and you can be a healthy kid.

1.You should eat different foods especially _______.

A .meat        

B. hamburgers    

C. sweets      

D. fruit and vegetables

2. Which kind of drinks can give you more calcium?

A. Juice.    

B. Milk          

C. Cold water.

D. Tea.

3. According to the passage, which of the following is TRUE?

A. When you're eating, you don't have to notice how your body feels.

B. You can eat your favorite food as much as possible.

C. You can watch TV whenever you like to get more information.

D. We should try to live in an active way in our life.

4. Which is the best title of the passage?

A. How to make yourself important.  

B. How to be a healthy kid.

C. How to be a popular kid.        

D. How to make your parents healthy.