You must know frictions. And, you probably can tell the roughness of surfaces is the reason why there are frictions. But, have you think about what happened micro-cosmically? I am pretty sure you would say no. So, let’s have a look.
http://umdberg.pbworks.com/w/page/46117252/Friction
Imagine you are pushing a heavy box. The bottom of the box may look smooth, but you will see many microscopic hills and valleys if you consider its micro-structure, so does the ground. Due to the gravity, the box is pushing the ground, so the hills of the box are pushed into the valleys of the ground, and vice versa. To move the box, there must be an applied force which is large enough to squeeze those hills and flat the surfaces. The resistance from the hills prevent being squeezed is known as frictions.
Frictions are very important in our life, but they also cause some wastes of energy. People have worked out many ways to minimize frictions.
https://www.youtube.com/watch?v=glXGDpEOU58
Video source( Flexiguru from YouTube)
Minimization of frictions benefits us a lot. The most representative achievement is maglev. Maglev trains are a transport method that uses magnetic levitation to move vehicles without contacting the track. For maglev, there is no friction between its wheels and tracks, so it can have a very high speed. The maximum speed of normal trains is around 300 km/h, but maglev can achieve 600 km/h which is 2/3 speed of civil airplanes. Moreover, maglev trains move more smoothly and more quietly.
The newest commercial maglev train was built in Shanghai. If you go to Shanghai, don’t miss it.
