Have you ever rubbed your hands together when they get cold? Why do we do that? We do that for friction. Friction happens when two things that aren't very smooth rub together to make heat energy. The faster you rub two things together, the more friction (and heat) you can make. Let's discover friction!

Are You Right Handed or Left Handed?

    Which hand do you use when write? About 8 to 15 percent of people are left handed. They often have to use tools that are designed for right-handed people. So it is difficult for left-handers to use most tools. If you are right handed, try this experiment: Take a knife with your left hand and try cutting a potato into pieces. Don't be surprised if you feel awkward（别扭的）.

    In the past, people thought it was strange to use the left hand. Young students looked down upon their left-handed classmates. Some children were even punished for using their left hand to write. But these days parents and teachers have accepted that. In almost every school in the world, left-handed students can use their left hand to write.

    What causes people to be left handed or right handed? Experts have searched long and hard on this. They conclude（得出结论） that left-handed people are left handed for the same reason that right-handed people are right handed. One out of every ten people just is a left-handed people are right handed. One out of every ten people just is a left-hander. It's simply like the color of our eyes – some people have brown eyes, while some others have black eyes.

    However, may researchers think that left-handers and right-handers are different in some aspects. Right-handers are more talkative and outgoing than left-handers. Many right-handed people understand spoken words better. For example, after they listen to directions to a supermarket, they can find it easily. Right-handers are good at organizing people, too. They are also better basketball guards. Just ask Yao Ming.

    Research shows that left-handers are creative and artistic. Many famous performers, like Jim Carrey and Paul McCartney, are left handed. Many left-handers learn better visually（在视觉方面）. In art, both Leonardo da Vinci and Michelangelo were left handed. In music, Ludwig van Beethoven was left handed. In science, you find Newton and Einstein. The left-handed people are also really good at tennis and other single sports.

    If you prefer one hand, but you are still good at writing with the other, you are mixed. Research shows mixed-handers can remember everyday things better than other people. What did you eat for lunch two weeks ago? If you're mixed handed, you can probably remember.

    In recent years, a number of Chinese technological innovations (科技创新) have been making waves around the world. Among them, four stand out. They are known as "four new great inventions of modern China. They have made our daily lives more convenient.

    High-speed trains

    China created its first high-speed railway line in 2008. Since then, the number of passenger trips has grown by over 30 percent every year. By 2016, more than 5 billion trips had been taken on China's bullet trains(高铁), according to Xinhua News Agency.

    China is currently working on the next-generation bullet trains that will have a top speed of 400 kilometers per hour. By 2020, one-fifth of the country's 150, 000-km railway network will be used by high-speed trains. This network will link more than 80 percent of major cities across China, said Xinhua.

    Mobile payment

    Mobile payment is turning China into a "cashless society" led by the third-party payment companies like Alipay. For example, instead of paying by cash, customers now pay for goods simply by typing a short password into Alipay app on their mobile devices.

    Users can also pay their bills through Alipay, such as their water and electricity bills. Alipay also supports cross-border(跨境的)online and in-store payment, which allows users to buy things on international websites and apps.

    Shared bikes

    Shared bike services started in Western countries. But China has surprised the world with how

quickly it has adopted dockless(无柱的) shared bikes.

    Unlike traditional bike-sharing method, dockless bikes allow users to simply pick up or park a bike on the street through GPS and smartphone app.

    To unlock a bike, you just need to scan a QR code on a shared bike with a smartphone app. After you finish riding, you can park it at available parking areas, lock it and pay for ride through mobile payment services.

    Online shopping

    With around 751 million internet users, China has been the world's largest and fastest-growing line shopping market.

    Online shopping now accounts for 15. 5 percent of total retail sales in China, according to Xinhua. Thanks to lower costs and fewer licensing requirements(执照要求), it's easier for sellers

to open an online shop in China than a brick-and- mortar shop(实体店).

    It also helped to create jobs of rural areas. In 2016, online shopping created more than 20 million jobs in rural areas, with over 8. 1 million running their own online shops, said Xinhua.

    Like most of her friends, Georgie Sanderson has 24-houpa-day access(使用权) to technology through her mobile phone, iPod Touch and home computer. But the 15-year-old girl says she is too busy to spend her days on Facebook. She only uses it once or twice a day. "The 10th grade is busy, and I have to work hard. Even when I'm not studying, I have better things to do with my time, such as being outside or spending time with my friends," she says. Georgie has a part-time job. She watches TV for a while in the afternoon and she helps with the housework.

    Georgie's words prove the findings of a new report. According to the report, teenagers today are not completely dominated(支配) by technology, although they have been into a digital(数字) world. They spend most of their time on their homework, TV, part-time jobs, hobbies, sports, friendship or reading instead of playing or chatting on the computer. But the report also finds that mobile phones are important to teenagers. 95 percent of 18 year-olds have got one mobile phone, and 82 percent sleep with their mobile phones on and beside them all night.

    For Georgie, sleep is more important than texting others. Georgie is also careful about the use of IT. She says, "Social media is helpful, but it is so distracting(使人分心的). I only use it when I do need to use it."

    Sometimes people call each other “scared-cat”, but have you ever thought about this expression? When a cat is frightened, its heart starts beating faster, its muscles get tense (紧张的), and there are changes in the chemicals in its bloodstream. Although the cat doesn't realize this, its body is getting ready for action. If the danger continues, the animal will do one of two things. It will protect itself, or it will run away as fast as it can.

    Something like this also happens to people. When we are excited, angry or scared by other feelings, our bodies go through many physical changes. Our hearts beat faster, and our muscles get tense. All of these changes make us more alert and ready to react. We, too, get ready to defend ourselves or run.

   Human beings, however, have a problem that animals never face. If we give way to our feelings and let them take over, we can get into trouble. Have you ever said something in anger — or hit somebody — and regretted it later? Have you ever shouted at a teacher, told somebody you were lonely, or said you were in love, and then wished later you had kept your mouth shut? It isn't always clever to express your feelings freely.

    Does this mean that it's smarter always to hide (藏) our feelings? No! If you keep feelings of anger, sadness hidden away or bottled up inside, your body stays tense. Physical illness can develop. It can actually be bad for your health. (It isn't good to keep pleasant feelings inside either; all feelings need to be expressed.)

    Feelings that you keep all bottled up inside don't just go away. It's as if you bought some bananas and stuck them in a cupboard. You might not be able to see them, but before long you'd smell them. And if you opened the cupboard, chances are you'd see little fruit flies flying all over them. They'd be rotten (腐烂).

    You can try to treat feelings as if they were bananas in the cupboard. You can hide them and you can pretend they don't exist, but they'll still be around. And at last you'll have to deal with them, just like those bananas.