HomePhysicalWhy is the dust in the back of the car a lot

# Why is the dust in the back of the car a lot

When the weather is dry, we often see: behind a fast-moving bus, there’s always dust on it. The car has already run away, so the dust has disappeared. What is the reason?
In the animal world show on TV, we often see a scene like this: in the vast sea off the coast, a huge whale swam in. Behind it, bubbles swelled up. If the small fish is swimming, the water surface will not ripple. That’s because the whale is very big, occupying a very large place in the water. When it swims forward, the spot where it leaves will immediately rush in. So in the tail of the whale, large waves often appear. As for the small fish’s volume, the amount of water added to it leaving is also very small, so it can not ripple bubbles.

Along with that cause, buses also occupy a certain space. When running, it pushes out the amount of air in such a volume. As the bus drove ahead, the place where the body was passing immediately had additional air. Therefore, the air on the sides and back rushed into it, forming a vortex and swirling air carrying dust on the road, sticking to the car’s rear. Therefore, we often see dust everywhere. At that time, if we open the car’s back window, the air will bring dust into the car. Therefore, the rear window of the bus is mostly locked, unable to open.

As for people walking, there is no dust behind them. It is like a baby swimming in water cannot ripple. The human volume is relatively small, the air pushed out is also relatively small, adding people’s walking speed not as fast as cars. So when we’re on the road, there’s no need to worry about the dust being followed.

James Smith
I used to look up at the sky when I was a child and wonder what's in those stars. Growing up, when I had the opportunity to contact the source of human knowledge, I had more knowledge about the universe, the natural world, and created laws. Being the founder of Wikiwap is where I can share my understanding of the world around me in a simple way that readers can access knowledge like a child. You and I are parts of the world; life will always be beautiful.