按照要求作图：

（1）根据图1中通电螺线管，在磁感线上标出方向，并标出电源的右侧小磁针的N、S极．

（2）如图2所示，杠杆在力F₁、F₂作用下处于平衡状态，L₁为F₁的力臂．请在图中作出F₂的力臂L₂及力F₁．

（3）如图3所示，a、b分别为一束入射光线和一束出射光线．请画出a经过凹透镜后的折射光线和与b对应的入射光线．

课外阅读。

竺可桢的故事

      竺可桢不仅爱学习，还爱用脑子思考问题。家乡雨水特别多，屋檐上老是滴水，落在石板上发出“滴滴答答”的响声。竺可桢站在一旁数那滴答作响的水滴，数着数着，他像发现了奇迹，眼睛盯住石板出神，他心里纳闷：哎，这些石板上怎么有一个一个的水坑呀，水滴正好滴在小坑里。再看看另外一块石板，也是同样的情况。他立即跑去请教父亲。

      竺嘉祥听了儿子的问话，由衷地高兴，耐心地向他解释说:“小熊啊，这就叫‘水滴石穿’呀！别看一滴一滴的雨水没有什么厉害的，但是，天长日久，石板就被滴出小坑了。读书、办事情，也是这个道理，只有持之以恒，才会有所成就。”

多项式 $36x^2-3x+5$ 与 $3x^3+12m{x}^2-5x+7$ 相加后，不含二次项，则常数 m 的值是（   ）

    Travelling is very interesting. Many people love travelling.There are many ways to travel：by plane，by train，by ship or by car. Everyone has their favourite way.

    Greg：My favourite way of travelling is by car. I can bring my pet dog along. I can travel three hundred miles or only fifty miles a day. I can stop at a good restaurant to enjoy a good meal or at a hotel to spend the night.

    Eliza：I love travelling by train best! It's very exciting. I travelled most of Europe in 5 months by train. It's the best way to talk with the local people and make new friends on the way. Trains make the long trip enjoyable. The train ride to me is just like a big moving party.

    I also like travelling by ship. It is a very great way to spend a holiday. I can go to parties and watch movies on the ship，and enjoy the blue sky and water.

    Danny：Travelling by plane is my favourite. It's the fastest way. I can quickly get to another country. Planes have very comfortable seats. I can have something to drink and eat. I can also read some free magazines and newspapers.