题干

“蹦极” 是一项刺激的极限运动,一个重为F0的运动 员将一端固定的长弹性绳绑在踝关节处,从高处跳下,测得弹性绳的弹力F的大小随时间t 的变化规律如图所示。若将蹦极过程视为竖直方向上的运动,且空气阻力不计。下列说法正确的是  ()
 

A:t1-t2时间内运动员处于超重状态

B:t1-t3时间内重力对运动员做功的功率越来越大

C:t1-t3时间内运动员的重力势能与弹性绳的弹性势能之和不断减小

D:t1-t5时间内运动员的机械能先减小后增大

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D

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How to Be Healthy and Happy

    We all want to be healthy, happy, free of stress and more productive in life.

    ⒈Get enough sleep. It not only keeps you healthy but also you will be happier. It is said that “Early to bed, early to rise makes a man healthy, wealthy and wise.”____

    ⒉Drink plenty of water. ____ The benefits of water are amazing. Water helps keep your skin clear, leaving you feeling happier and better about your body. Water is just simply an amazing source in itself for your overall health. Try to drink 8 glasses a day.

    ⒊Smile and laugh. Don't get sad over small problems or take any joke seriously which hurt you. Instead, if you feel so hurt, you prefer to stay away from that friend. ____ Respect your friend from a good perspective. Smile and laugh all the time and you will be happy.

    ⒋____Help your mom do the dishes, help out your dad in the kitchen, clean your room, or do anything that could help your family. It will not only make them love you more, but you will feel happy knowing you have done good even if you moved out twenty years ago and are a father yourself.

    ⒌Have goals. Always believe you can achieve. If you can dream it, you can achieve it, no matter what. ____ Organization plays a very important role in achieving goals, so organize yourself.

A. Help out your family.

B. Don't get in touch with him/her.

C. So make sure you go to sleep earlier.

D. Of course keep goals and dreams realistic.

E. Water is good for everything in your body.

F. The majority of our body is made up of water.

G. However, don't show him that you don't like him.