“Drifting with water” is one of the oldest games played by human beings. It refers to the use of flat tiles or stone flakes, placed horizontally on the hand and then thrown forcefully. water surface and fly. Once the coin hits the water surface, it bounces and flies again. The piece of stone continues to bounce on the water surface until its inertia is exhausted, then sinks.
It's different from throwing a stone directly into the water. We often choose the shape of the stone, and the angle and strength of the throwing method will affect the number of times and the distance in which the stone floats in the water. END. Has a huge impact.
So, what is the principle? What angle, what type of stones and what force can cause the water to drift further?
Physical explanation
The stone flies towards the surface of the water at a certain speed. Part of the liquid in contact withirect with the stone acquires the same speed as the stone in a short time. under the action of viscosity, compared to the liquid in the lower layer which is not in direct contact, the upper layer moves faster according to the Bernoulli principle, where the flow rate is high, the pressure is low and the liquid pressure is low. The lower layer of liquid is stronger than that of the upper layer of liquid, generating upward pressure. This pressure can be reduced to zero and accelerated in the opposite direction to generate upward velocity. an upward projection movement. The above is a qualitative explanation of the formation of a water float.
Bernoli's principle
Obviously, only by reducing the stone's own gravity as much as possible and increasing its buoyancy, i.e. pressure generated by the pressure difference, that the stone can float more. When you launch a smallte stone, you should choose a small stone as flat as possible to increase its buoyancy and reduce its own weight. At the same time, you need to throw it at a shallow angle to get more lateral speed and reduce it. vertical speed. Of course, the graphical model is oversimplified. In order to obtain more precise results, more precise analysis and support from experimental results are necessary.
What is the best swimming posture?
A 2004 Nature article presented the secret to success: the mysterious 20° angle. The angular speed of rotation of the stone can make the movement of the stone more stable and keep the angle of attack constant as much as possible. The principle is the principle of a gyroscope and the conservation of angular momentum [3]. Therefore, the greater the angular speed of rotation, the better. As for the shape of the stone, according to experience, a diskdish is the best.
So all the factors for successful flotation on water: use flat disc-shaped stones, the angle of attack should be 20° as much as possible, plus the angular velocity of rotation is greater, the better and the greater the angular speed of rotation. the speed of the projectile, the better.
This story is widely spread. This probably means that you take out a cup first, then put stones in the cup. If the cup is full of stones, the host will ask you if this is the case. complete? Most people will subconsciously answer “complete.” Then the host puts sand on it. If it is full of sand, the host will ask if it is full. By then everyone knew their routine and knew other things could be included. Then put more water in it. When the water is full, does that really mean it is full? It is said that we can also addethanol.
The story is the same, but different people use it to illustrate different truths.
And I want to ask: put the stones in first and thenPutting sand in is the same amount of sand as putting sand in first? Putting the stones and sand first, then the water is the same as putting the water first. Are the two quantities of water the same? If it's the same amount of water, why not put the water first then the stones and sand?
Human life is too long, so let's reduce it to one day.
Stones, sand and water respectively represent what we have to do during the day. For example, stones represent study, sand represents fun, and water represents rest. The time we use to rest during the day is almost fixed, and it doesn't matter if we rest first or later. The sand must be placed after thelaying stones. What is put here is the sequence, doing the most important things first and putting the things that need to be done first.
Stones, sand and water can also represent other things. We should put what we value most at the forefront and those that are unnecessary at the bottom. For example, if we like sand the most, we can put sand first. We also need a certain amount of stones, so we don't need to fill them with sand and leave a certain space for the stones. If we like water the most, we can put the water first. If we need a certain amount of sand and stones in addition to water, just leave room for them.
First plan how many stones, how much sand and how much water we need, then choose which ones should be guaranteed in quantity and which ones can beadded or subtracted. If we need more water than adding a little, we can't wait until the end to release the water.