题干

如图所示,竖直光滑杆上套有一个小球和两根弹簧,两弹簧的一端各与小球相连,另一端分别用销钉M、N固定于杆上,小球处于静止状态.设拔去销钉N瞬间,小球加速度的大小为12m/s2.若不拔去销钉N而拔去M销钉瞬间,小球的加速度可能是?(取g=10m/s2

上一题 下一题 0.0难度 选择题 更新时间:2017-10-20 10:05:41

答案(点此获取答案解析)

解:设上下弹簧的弹力大小分别为 F1,F2 ,两个弹簧所处的状态可能分为两种情况:①上下弹簧是压缩的,则

同类题1

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。

    ____

    Self-worth is very important in your life. We may love others, but we need to learn to love ourselves. We have to believe in what we do, and feel better about ourselves. If you do not have self-worth, you may begin to get discouraged.

    Avoid negative people in your life. ____If these people put you down, do not believe in you, or treat you badly, why are you still around them? It took me years to realize this for myself, and it is true. Negative people hurt your self-worth, and bring you down emotionally. Get closer to people that believe in you. If you do not have these positive people in your life, find a support group that can help you. ____Your self-worth can be increased greatly with positive guide.

    Find employment or volunteer somewhere you feel valued, or can make a difference. Giving to others builds you up personally. You do not have to do this all the time, but once you see how good it feels you will want to continue.

    ____Think about what you can do to change your future. Make a list of steps you can take to improve your life. Stall setting goals in your life. Goals give us something to focus on, and we push to achieve them. These can be whatever goals you would like to finish, be sure they are achievable Goals. ____

    Doing the above steps can greatly increase your self-worth, and remember you are worth it.

A. Stop thinking about the past as you can't change it.

B. Keep the saying of "No pain, no gain" in mind.

C. Increase Your Self -Worth and Feel Better about Yourself.

D. Believe You can Be the King of the World Even When You Fail.

E. Once you set your goals, you will start pushing for more.

F. These people are likely to believe in us even when we do not have confidence.

G. This could be your husband, boyfriend, other family members, or even friends.

同类题3

根据短文内容,选择正确答案。

B

    Sam was a fifteen­year­old boy living with his little sister, Julie. Their parents passed away long ago. Sam had to take care of Julie by himself.

One day, Sam woke up at three in the morning as usual. When Julie was sleeping alone, Sam left their little house to send newspapers. When he found an old man sitting in front of their house, Sam was so surprised that he stopped to look at him closely. It was an icy morning and he looked very cold.

    The poor old man didn't have anything to cover himself with. Sam went into his house to get the old man a blanket(毯子). However, there were no extra blankets, so Sam thought hard and took his father's coat. It was the only thing of his father's that he had left. Sam wrote a short note. "Sir, I found you sleeping in front of my house. This is my father's coat. I hope it fits you well." He put the note in a pocket of the coat and covered the old man with the coat. Then he went to work. When he came back, both the man and the coat were gone. Sam thought that it was the best thing he could do with his father's coat.

    That afternoon, Sam hurried home after school because Julie was at home alone. However, Julie and the old man were standing in front of the house, and Julie shouted to Sam, "Brother! He's our grandfather!"

    The grandfather smiled and said, "Sam, thank you for giving me the coat and letting me know how good my grandson is. This coat was the one that I gave my son a long time ago!"