Structural diagram and principle of the hottest ja

2022-10-19
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The structure diagram and principle of Jack

there was no toothpaste tube in the 17th century. Therefore, people doubt whether Blaise Pascal (Blaise PA is released during the time period to meet the flow required by the load, scal, 1623-1662, a famous French scientist and philosopher) has put forward Pascal's principle, and whether he is thinking about its function every morning

however, it is certain that many other effects related to hydrostatic pressure cannot escape his attention. The first is the principle of hydraulic crane

engineers used this type of machine a long time ago. Today, as long as you are in a parking lot or gas station, you can see a hydraulic crane, which can lift a car with the strength of a child. Let's see how this device works and try to make one of our own for experiments

see Figure 2. Connect two containers filled with liquid (water or oil) with a pipe hand. One of the containers has a large section, while the other has a small section. Suppose it is 1000 times smaller than the previous section. If a piston (a) is used to press down the liquid level of the container with small cross-section, the liquid will receive a pressure, and the strength of this pressure will be transferred to any other part of the liquid surface according to the original size, including, of course, the surface of the liquid in contact with the piston (b) in the container with large cross-section. The pressure is equal to the force divided by the area of action

according to Pascal's principle, the pressure under piston a is equal to that under piston B. since the area under piston B is 1000 times larger than that under piston a, the force on it should be 1000 times larger than that on piston a. Therefore, in order to lift a 1-ton car, only 1 kg of force is enough. Hydraulic brakes, compressors, car jacks, water pumps and many other devices benefit from this principle

small experiment to verify Pascal's principle

using two syringes without needles, we can make a small hydraulic device of this kind at home

for example, use a thick syringe with a cross-section of 5 square centimeters for blood transfusion and a very small syringe with a cross-section of 0.5 square centimeters to connect their openings with thick and short tubes. According to Pascal's principle, the conversion coefficient of force is about 10. Fill the syringe with water, oil or other liquid, that is, all the space between the two pistons, and pay attention to eliminate the bubbles. Then ask your friend to squeeze one of the two pistons with your thumb while squeezing the other piston with your thumb. We can call this little game the contest of iron thumb, or Pascal thumb. Of course, whoever squeezes a small syringe will win without effort. If you have a certain creativity and ability to do experiments, you can use a spring dynamometer or a weighing scale (as shown in Figure 3) to try to measure the pressure exerted when squeezing two pistons, so please regularly check the pressure exerted by one of the pistons (or use a weight that weighs more than the friction between the piston and the syringe tube wall), verify Pascal's principle, and see whether the pressures on both sides are equal. Don't forget to subtract the existing value before squeezing the syringe from the measured value, which is equivalent to the active part of the system, that is, the liquid plus the weight of the piston

finally, if you want to verify the efficiency of this device as a pressure device, you can put a walnut between the scale plate and the large piston: you will see that squeezing the piston of the small syringe can easily crush the walnut

with this small machine, you can accomplish great things like Hercules (the son of Zeus, who has accomplished 12 heroic achievements). If you are ready to take an ordinary belt and put a closed bucket full of liquid (don't leave air, because the air will be compressed under pressure), you can start demonstrating to your friends. Connect the wooden barrel full of liquid with a small syringe also full of liquid and Wiggins, etc. in hydrogen peroxide and 2 cobalt chloride solution for in vitro dynamic test. You will see that the latter two can break the wooden barrel instantly. We try to calculate an account: an ordinary syringe with a cross-section of 0.5 square centimeters, the pressure exerted by the thumb on the piston is 20 kg (verified by the scale, it is not difficult to reach this weight), and the pressure turned out to be 40 atmospheres! Few wooden barrels can withstand such pressure. A farmer regretfully found this phenomenon. He wanted to transport the precious wine from his rural farmhouse to a friend's house at the foot of the mountain more than 30 meters low through a long thin pipe. Everything went well: a friend's wine barrel was full of wine, but then the pressure in the liquid pipe soon broke the barrel, and the wine soaked the house

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