问题 选择题

如图,在距地面h高处以初速度v0沿水平抛出一个物体,不计空气阻力,物体在下落过程中,下列说法中正确的是(  )

A.物体在c点比a具有的机械能大

B.物体在c点比a具有的动能小

C.物体在a、b、c三点具有的动能一样大

D.物体在a、b、c三点具有的机械能相等

答案

A、沿水平抛出一个物体,不计空气阻力,物体在下落过程中,只有重力做功,机械能守恒.

所以物体在a、b、c三点具有的机械能相等,故A错误,D正确.

B、根据动能定理得物体在下落过程中,重力做正功,动能增加,所以物体在c点比a具有的动能大,故B、C错误

故选D.

单项选择题 A1型题
阅读理解

阅读理解。

     Anorexia (厌食) and bulimia (食欲过度) are the names that come to mind when we think of eating

disorders (失调). But there is another eating disorder more common than anorexia and bulimia, and some

experts say it's becoming a major health problem in America.

     "As soon as I came home, I'd throw down my backpack, open the refrigerator and start eating.

Sandwiches, cookies, candy bars -I'd just eat until I went to bed," says Matt Wymer, 18.

     Matt was a binge (无节制的) eater. According to a new study from Harvard Medical School, 3.5

percent of women and 2 percent of men suffer from this eating disorder.

      "You know we start at a very young age. You fall and someone says, 'Oh, here, we'll go get some ice

cream, and that'll make it feel better. ' Or when you go to the doctor, you get a candy; something bad

happens, 'Oh, here's something that's comforting,'" says Marilyn Tanner, a doctor.

     Matt looked for comfort because he was always teased (嘲笑) about his weight.

     "There were days when I came and picked him up from school and he got in the car and he started crying

before I asked him anything," says Cathy Wymer, Matt's mother."I probably gave him whatever he wanted

to try to make him happy, but it was the wrong way of doing it." says Matt's father.

      "I just felt better after I ate a lot," says Matt.

      Experts say the first line of treatment for binge eaters is to help them find other ways, besides food,

ot feel better."There are about five basic ways. You write, you talk, you cry, you exercise, you laugh.

Laughing also reduces the stress that lots of times people are feeling," says Genie Burnett, Matt's doctor.

     With the help of his doctor, Matt started a diet and did much sport. He's lost more than 150 pounds,

he's healthier and he says he's more confident.

1. What would be the best title for this passage?

A. Matt's interesting life.

B. Matt's parents' worries.

C. Eating disorders.

D. Binge eating.

2. From the second paragraph know that Matt ______.

A. is very busy at home every day

B. goes to bed very late at night

C. suffers from an eating disorder

D. is not good at his lessons.

3. According to Marilyn Tanner, it is true that ______ .

A. eating disorder begin at an early age

B. ice cream is popular with most children

C. young children fall and hurt their knees easily

D. crying is a good treatment for binge eaters

4. Matt has become more confident by ______.

A. talking

B. laughing

C. exercising

D. writing