I went sightseeing in a university. I went to the mechanical and engineering department. The day was an open day of the university , so there are some professors greet people and they show some particular small experiment or theory to us! I think I probably got into the mechanical and material engineering. They show some materials, aluminium, and an alloy of aluminium and copper. The professor told me that the alloy was very strong and is used for making aircraft. No one use a pure aluminium metal. He told me that it is strong because the copper added increased the resistance. The model of the alloy metal slides too but not for the whole row. Ya. That moment, I knew about the resistance not only in electricity but also in the strength. He used a term' line' to describe the boundary. Is anyone free to explain further? Then he brought us to another room. He used immersed one iron metal into liquid nitrogen. Do you know the purpose? The iron is very cold. Then he use some equipment to measure the energy required to break this iron and another iron not immersed.(The central of both iron metals have a small valley) I know you must know the result The professor spilt the container and the liquid nitrogen was spilt. The spread was so fast. What I saw was, the colourless liquid touches the floor and evaporate very fast. The metal cover stained with some liquid. The surface turned into ice! The process was very smooth, I was very excited to have an experience on this dangerous chemical! The circumstance like a scenery in the " The Day after tomorrow". The scenery of the US flag turns into ice and the temperature of the surroundings drop at a rate of 10 Celsius degree. So you know how excited I was! Luckily, no one was hurt. Something more is the professor is an indian, I think(Since some of the english he spoke liked an indian and I couldn't hear clearly.My english is not very good so I am not sure).Third, we moved into a room. He put two long steel into a hot furnace. Then he put one of it into water and the other was left to cool down in air. He pointed a girl to break the steels. Could anyone predict the result and explain it ? I am not very sure in the explanation.(He didn't explain ) Then, I went to the fluid visualisation mechanics. A car with shelter in a box. Something I want to consult is, whether the car behind a car need to spend more energy to run or spend less energy. The day spent there last me over 5 hours. Maybe I would share them later! I put my thread here because I think I need someone's help.