如图是小龙探究“杠杆平衡条件”的实验装置，用弹簧测力计在C处竖直向上拉，杠杆保持平衡。若弹簧测力计逐渐向右倾斜，仍然使杠杆保持平衡，拉力F的变化情况是

    Chinese are very generous (慷慨) when it comes to educating their children. Not caring about the money, parents often send their children to the best schools or even abroad to England, the United States or Australia. They also want their children to take extra-course activities. The Chinese believe that the more expensive an education is, the better it is.  However what most parents fail to realize is that today's children lack self-respect and self-confidence.
    Parents can achieve this by teaching practical skills like cooking, sewing and doing other housework.
    Cooking demands (要求)patience and time.  A good cook always tries to improve his cooking. so he will learn to work hard and gradually(逐渐), finish his job successfully.  His result, a well-cooked dinner, will give him much satisfaction and a lot of self confidence.
    Some old machines, such as a broken radio or TV set that you give your child to play with will make him curious and arouse his interest. He will spend hours looking at them, trying to fix them; your child might become an engineer when he grows up.  These activities are not merely   teaching a child to read a book, but rather to think, to use his mind. And that is more important.

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    Do you know how to play a game called “Musical Chairs”? It is easy to play and most people enjoy it. All you need are some chairs, some people and some ways of making music. You may use a piano or any other musical instrument, if someone can play it. You may use a tape recorder. You can even use a radio.

Put the chaffs in a row. The chairs may be put in twos, back to back. A better way is to have the chairs in one row with each chaff facing in the opposite direction to the chair next to it.

    The game is easy. When the music starts, the players walk round the chairs. Everyone goes in the same direction, of course, they should walk in time to the music. If the music is fast they should walk quickly. If the music is slow, they should walk slowly.  

    The person playing music cannot see the people in the game. When the music stops, the players try to sit on the chairs. If a person cannot find a chair to sit on, he drops out: Then, before the music starts again, one chair must be taken away. When the music stops again, one more player will be out.

    At last, there will be two players and one chaff. The one who sits on the chair when the music stops is the winner.