阅读理解。
Just as adults have a hard time putting down their iPhones, so the device is now the toy of choice for
many 1- 3 years old children. It's a phenomenon that is attracting the attention of some childhood
development specialists.
Natasha Sykes, a mother of two in Atlanta, remembers the first time her daughter, Kelsey, then
barely 2 years old, held her husband's iPhone. "She pressed the button and it lit up. I just remember her
eyes. It was like 'Whoa!' "The parents were charmed by their daughter's fascination. But then, said Ms.
Sykes, "She got serious about the phone."Kelsey would ask for it. Then she'd cry for it. "It was like she'd
always want the phone," Ms. Sykes said.
Apple, the iPhone's designer and manufacturer, has built its success on machines so simple and
intuitive(直观的) that even technologically confused adults can figure out how to work them, so it makes
sense that expert children would follow. Tap a picture on the screen and something happens. What could
be more fun?
Many iPhone on the market are aimed directly at preschoolers, many of them labeled "educational,"
such as Toddler Teasers: Shapes, which asks the child to tap a circle or square or triangle; and Pocket
Zoo, which broadcasts live video of animals at zoos around the world.
There are "flash cards" aimed at teaching children to read and spell, and a "Wheels on the Bus"
program that sings the popular song in multiple languages. Then there's the new iGo Potty program, with
automated phone calls reminding toddlers that it's time to "go ".
Along with fears about dropping and damage, however, many parents sharing iPhones with their
young ones feel guilty. They wonder whether it is indeed an educational tool, or a passive amusement like
television. The American Academy of Pediatrics has long advised parents not to let their children watch
any TV until they are past their second birthday.
Jane M. Healy, an educational psychologist in Vail, Colo. said: "Any parent who thinks a spelling
program is educational for that age is missing the whole idea of how the preschool brain grows. What
children need at that age is whole body movement, the skills of playing lots of objects and not some
difficult technology. You're not learning to read by lining up the letters in the word 'cat.' You're learning to
read by understanding language, by listening."
1. The main purpose of Kelsey referred to in the passage is to ____.
A. not only adults but children are crazy about iPhones
B. encourage people to buy this toy for their children
C. advertise for the toy
D. show Kelsey likes the toy very much
2. The underlined words "it's time to 'go' "in Paragraph 3 mean ______.
A. it's time to stop playing the toy
B. it's time to go to sleep
C. it's tie to go to the washroom
D. it's time to go home
3. The parents asking their young children to play iPhones feel guilty because _____.
A. they know the toy has a negative effect on them
B. the children damage the toy
C. they are not sure of the real effect of the toy
D. they ask their children to watch live video of animals
4. In Jane's mind, in educating preschoolers parents should _____.
A. buy this toy for their children.
B. ask their children to play as many toys as possible
C. ask their children to learn a spelling program
D. know how the preschool brain grows
的固定的光滑斜面的顶端A滑至底端B，A点距离水平地面的高度h=5.0m，重力加速度g取10m/s2，(sin37°=0.6，cos37°=0.8)，试分析：
何时重力的功率最大，其值是多少.
mｖＢ２………………①
="10m/s " ………………②
－θ）…………③