问题 不定项选择

如图所示,一绝缘光滑半圆环轨道放在竖直向下的匀强电场中,场强为E在与环心等高处放有一质量为m、带电+q的小球,由静止开始沿轨道运动,下述说法正确的是[ ]

A.小球在运动过程中机械能守恒

B.小球经过环的最低点时速度最大

C.小球经过环的最低点时对轨道压力为3(mg+qE)

D.小球经过环的最低点时对轨道压力为(mg+qE)

答案

BC

单项选择题
阅读理解

根据短文内容,从短文后的选项中选出能填入空白处的最佳选项。选项中有两项为多余选项。

A good book can be satisfying. If reading is a habit you’d like to get into, there are some ways to develop it.

Realize that reading is enjoyable if you have a good book. If you have a difficult book and you are forcing yourself through it, it will seem like a task. 小题1:_____________

Set time. You should have some time during every day when you’ll read for at least 5 to 10 minutes. 小题2:____________ For example, make it a habit to read during breakfast and lunch and even dinner if you eat alone.

Always carry a book. 小题3:____________ When I leave the house, I always make sure to have my car keys and one book at hand. The book stays with me in the car, and I take it into the office and to appointments and pretty much everywhere I go.

小题4:_______________ Find a place in your home where you can sit in a comfortable chair. Don’t lie down unless you’re going to sleep. There should be television or computer near the chair, and no music or no noisy family members/roommates. If you don’t have a place like this, create one.

Reduce television/the Internet. If you really want to read more, try cutting back on time on TV or the Internet. 小题5:____________Still, every minute you reduce of the Internet/TV, you could use for reading. This could create hours of book reading time.

A.Wherever you go, take a book with you.

B.Go to bookstores.

C.Have some good tea or coffee while you read.

D.Find a quiet place.E. This may be difficult for some people.

F. If this happens, give up the book and find another one that you’ll really love.

G. It means you will read no matter how busy you are.