问题 选择题

如图所示光滑竖直圆槽,AP、BP、CP为通过最低点P与水平面分别成30°、45°、60°角的三个光滑斜面,与圆相交于A、B、C点.若一物体由静止分别从A、B、C滑至P点所需的时间为t1,t2,t3,则(  )

A.t1<t2<t3

B.t1>t2>t3

C.t1=t2=t3

D.t1=t2<t3

答案

设任一斜面的倾角为θ,圆槽直径为d.根据牛顿第二定律得到:a=gsinθ,斜面的长度为x=dsinθ,

则有:x=

1
2
at2

   t=

2x
a
=
2dsinθ
gsinθ
=
2d
g

可见,物体下滑时间与斜面的倾角无关.则有t1=t2=t3

故选C

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。

Happiness is the only true measure of personal success. Making other people happy is the highest expression of success. 小题1: With that in mind, here are some suggestions that will immediately increase the amount of happiness in your life:

小题2:

If there’s any big truth about life, it’s that it usually lives up to your expectations. Therefore, when you rise from bed, make your first thought: “Something wonderful is going to happen today. Guess what? You’re probably right.

Take time to plan and prioritize (优先处理).

The most common source of stress is the thought that you’ve got too much work to do. Rather than worry about it, pick one thing that will move you closer to your highest goal and purpose in life. Then do that first.

Eat high quality food slowly.

小题3: Even so, at least once a day try to eat something really delicious, like a small chunk of fine cheese or and imported chocolate. Taste it, focus on it and enjoy it.

Let go of your results.

The big enemy of happiness is worry, which comes from focusing on events that are outside your control. Once you’ve taken action, there’s usually nothing more you can do. 小题4:

End each day with gratitude.

Just before you go to bed, write down at least one wonderful thing that happened. It might be something as small as making a child laugh or something as huge as a million dollar deal. 小题5:

A.Start each day with expectations.

B.Give a gift to everyone you meet.

C.Thinking about that thing makes your head hurt.

D.It’s impossible to make others happy if you’re not happy.E. Whatever it is, be grateful for that day because it will never come again.

F. Sometimes we can’t avoid eating something quickly and running.

G. Focus on the job at hand rather than some fantasy that might happen.

单项选择题 A1/A2型题