There are many physical phenomena in life, and many simple phenomena can be answered by what we have learned.
Phenomenon 1: The express train has a safe distance. We are walking on the expressway, so don't get too close to it except for fear that the off-line car will hit us. There is another unexpected reason, which this article will answer.
Phenomenon 2: Take two thin pieces of paper, stick them together and blow hard. We can't blow the paper away, but it will be blown away.
Phenomenon 3: With the same flow of water, the flow rate of large-caliber faucet water is very slow, but it can be clearly seen that the flow rate of small-caliber faucet is accelerated. What is the reason?
To sum up, air and water are both fluids, and they have some similarities, both of which follow the basic properties of fluids. There are two very important equations in fluid research: Bernoulli equation and continuity equation. These three phenomena can be easily explained by them. First of all, the basic expression of Bernoulli equation is: P+ 1/2pv+pgh= constant. P refers to the pressure around the fluid, P refers to the density of the fluid itself, and V refers to the velocity of the fluid. In the above phenomenon, water and air can be approximately regarded as ideal fluids, and they are constantly flowing. In the first two cases, pgh can be regarded as a constant, so we can easily get P+ 1/2pv= constant. It is easy to conclude that pressure is inversely proportional to speed. The following are for three people.
Give a concrete explanation to the phenomenon.
Explain phenomenon 1: One of the reasons mentioned is that the surrounding air is likely to "push" us into the car and cause an accident. Why do you say that? When cars pass by us quickly, it has an impact on the surrounding air: it speeds them up. In this case, according to the above, it is easy to know that because the speed is too fast, the pressure of the surrounding air decreases, forming a pressure difference around the car, and things around the car are easily "pressed" under the car. It's dangerous, so try to pull over on foot.
Phenomenon 2: When two pieces of tissue paper are close together, we regard them as isolated from the outside air. When we blow air, the speed of a little air between two pieces of paper increases and the pressure decreases, and the surrounding air makes the pieces of paper stick together.
Explain phenomenon 3: with the same flow and volume, it is easy to know SV = S V, which is the continuity equation of ideal fluid. This means that when the ideal fluid flows stably, the product of fluid velocity and cross-sectional area of the flow tube is a constant. So when we reduce the aperture, it will inevitably lead to an increase in speed. According to this principle, there are also great applications in science and technology, such as cutting water guns. With the same water output, this kind of water gun has a small caliber, which makes the water output very fast and contains a lot of kinetic energy.
It has great application in production.
Finally, we should introduce a very practical method: taking water. At home, I saw an adult put a pipe into the water and inhale through his mouth, and the water would flow out by itself. I tried, but it didn't work. Now I aim at the reason: the suction end must be lower than the water end. Why? This is based on the principle of atmospheric pressure. When the tube becomes vacuum after inhalation, the water is submerged by the external atmospheric pressure.
Physics plays a great role in our life. We can learn physics through life and then serve life with physics.