问题 选择题

在同一水平直线上的两位置分别沿水平方向抛出两个小球A和B,不计阻力,轨迹如图所示.要使两球在空中相遇,必须满足下列哪个条件?(  )

A.A球质量小于B球质量

B.A球先行抛出

C.B球先行抛出

D.两球同时抛出且A球初速度大于B球初速度

答案

由于相遇时A、B做平抛运动的竖直位移h相同,由h=

1
2
gt2可以判断两球下落时间相同,即应同时抛出两球,物体做平抛运动的规律水平方向上是匀速直线运动,由于A的水平位移比B的水平位移大,所以A的初速度要大.故D正确,A、B、C错误.

故选D.

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阅读理解

阅读理解

     Every day has just 24 hours - and this applies to all people. Some people are constantly pushed for

time. This article is about how we can learn to manage our valuable time more effectively.

     In reality we cannot manage time. We can only manage ourselves and our relationship with time.   1   

And habits are not that easy to changes.

     Below here are tips that can help you manage your time better.

     Organize your goals.

     Organize your goals based on two criteria: degree of urgency and importance: a. Should be done

today, tomorrow, etc. b. Should be done at "that date". c. Can be put off for so many days. d. Can ask

someone else to do it.    2  

     Clean up your list.

     Make a list of everything you think that is not helping or benefiting you and do not do them!

     Focus on one goal.

     Concentrate only on one goal at a time. Otherwise, if while dealing with something you think about

everything you can do later, most likely you will get bored and disappointed.    3   The boredom (厌倦)

is guaranteed with this way of thinking.

     Identify your deadlines.

        4   Divide the activities per day / week and long-term goals to get a clear

picture of what you have to do and when.

     Find suitable work environment.

        5  

     Be realistic.

     Make sure that your goals are realistic and do not try for the impossible.

     Say "NO".

     Learn to say "no" to other activities, requests and people who eat your time

     (unless indeed at that very moment it is necessary for you to help them).

A. Allow time to adjust your list if necessary.

B. After all, how we use our time is largely a matter of habit.

C. Create a suitable environment to work, one that fits your style.

D. Check the list of what you should do and when it must be completed.

E. After organizing your goals, start with the most important and urgent.

F. It is like every time you eat you think all the meals you must eat in your life.

G. Do not let boredom discourage you if what you have to complete is boring.