Why do you have to change gears when driving?

Most car gears are divided into one to five gears, plus a reverse gear. At present, many people don't know why drivers often change gears while driving. In fact, why do you want to change gears is the same as why students at school want to go to the next grade. When a student has finished the content of senior one and has the qualification of senior two, the teacher will naturally let him enter the classroom of senior two and attend the class of senior two.

The shift position is the same. There is a gear matching it at a certain speed. If it reaches a certain speed, it is necessary to shift to the corresponding gear. For example, the current speed is 20 kilometers, so the most suitable gear is the second gear. If you continue to step on the accelerator, when the speed rises to 30 to 40 kilometers, you will have to shift into third gear, because the speed at this time is most suitable for shifting into third gear. Similarly, if you continue to accelerate to forty or fifty kilometers, you will shift to fourth gear. Once it's over 50 kilometers, it's most appropriate to shift to the fifth gear.

In short, what kind of speed and what kind of gear are the best uses of the engine.