1: This is because the air above the flame is very hot, and then it convects with the cold air. However, the density of cold air and hot air is different, which leads to the different refractive index of light in cold and hot air, which leads to the bending of light when it passes through cold and hot air. You can think of air as a piece of thick glass that keeps moving. The glass is uneven, and you can see whether things are bent or not through the glass.

2. The ball can reduce friction; Because writing without ball is not smooth, the sense of resistance becomes greater.

3. Conversion: gasoline combustion-biological energy is converted into heat energy; After gasoline burns, it drives the engine to run-heat energy is converted into kinetic energy.

Transmission: Gasoline engines transmit heat energy to the air by emitting gas.