What is the Bo Effort Effect? The Magnus Effect and Bernoulli s Principle

In 1726, the Swiss scientist Bernoulli found that "when the velocity of a fluid increases on the same streamline, its pressure decreases." This is often referred to as the "Bo effort effect".

The subway radio will say "please stand outside the yellow line" over and over again, not for children, because the "Bo effort effect" produced when the train comes cannot even guarantee that adults will not fall down.

When the train moves forward at high speed, it also moves forward with the air around it, and people stand on the side of the railway, the air behind them is flowing at high speed, but the air in front of them is stationary, according to the "Bernoulli principle", the pressure of the still air greatly exceeds the pressure of the high-speed flowing air. So if you are very close to the tracks, people will be pushed down by the pressure of the air in front of them and reverse to the speeding train. Therefore, the purpose of the cordon is not to be afraid that people will be hit by the train, but to fear that when the train or subway passes quickly, it will "suck" people who are too close to the train, and they will either die or be injured, so people must stand outside the yellow line and "not take a step beyond the thunder pool".

The Magnus effect is a phenomenon in fluid mechanics in which when the rotational angular velocity vector of a rotating object does not coincide with the object's flight velocity vector, a transverse force is generated in the direction perpendicular to the plane composed of the rotational angular velocity vector and the translational velocity vector. Bernoulli's principle is essentially the conservation of mechanical energy of a fluid. Namely:

Kinetic energy, gravitational potential energy, pressure potential energy, constant. The most famous corollary is that when the flow is at a constant height, the flow velocity is high, and the pressure is small.

It is important to note that since Bernoulli's equation is derived from the conservation of mechanical energy, it is only suitable for ideal fluids with negligible viscosity and non-compressibility. Suitable for ideal fluids (no frictional resistance). The terms in the equation represent the difference between the kinetic energy, potential energy, and static pressure energy of the unit fluid.

The Magnus effect, named after his discoverer, Magnus, is a phenomenon in fluid mechanics that is a force exerted on an object (such as a cylinder) rotating in a fluid. The Magnus effect can be used to explain phenomena such as curveballs in table tennis, banana balls in football, and so on. In 1742, Benjamin Robbins, a British gun engineer, explained the deviation of the trajectory of a rifle projectile in the Magnus effect.

Daniel Bernoulli proposed the "Bernoulli Principle" in 1726.

This is the basic principle adopted by hydraulics before the establishment of the theoretical equations of continuum in fluid mechanics, the essence of which is the conservation of mechanical energy of fluids. That is: kinetic energy + gravitational potential energy + crushing resistance force potential energy = constant.

The most famous corollary is that when the flow is at a constant height, the flow velocity is high, and the pressure is small.

It should be noted that since Bernoulli's equation is derived from the conservation of mechanical energy, it is only suitable for ideal fluids with negligible viscosity and non-compressibility.

The use of Bernoulli's law must meet the following assumptions before it can be used; If the following assumptions are not fully met, the solution is also approximate.

Steady flow: In a flow system, the properties of a fluid at any point do not change over time.

Incompressible flow: the density is constant, and the Mach number (ma) is suitable for the < of the fluid as a gas.

Frictionless flow: The frictional effect is negligible, and the viscous effect is ignored.

Fluids flow along streamlines: Fluid elements flow along streamlines, and the streamlines do not intersect each other.

Daniel Bernoulli first proposed it in 1726 that in a stream of water or air, if the velocity is small, the pressure is greater, and if the velocity is high, the pressure is smaller. Of course, there are certain limitations to this original acre, but we will not talk about it here.

Here are some layman's explanations:

Blow air into the AB tube. If the cut of the tube is small (like a), the velocity of the air is greater; In places with large cuts (like B), the velocity of the air is smaller. There is less pressure where the speed is high, and more pressure where the speed is small.

Because the air pressure at A is small, the liquid in the C tube rises; At the same time, the relatively high air pressure at B causes the liquid in the D tube to drop.

The Magnus effect is a phenomenon in fluid mechanics in which a transverse force is generated perpendicular to the plane of rotation and translational velocity vector when the grinding angular velocity vector of a rotating object does not coincide with the vector of the object's flight velocity. Bernoulli's principle is essentially the conservation of mechanical energy of a fluid. Namely:

Kinetic energy spine gravitational potential energy Pressure potential energy constant. The most famous corollary is that when the flow is at a constant height, the flow velocity is high, and the pressure is small.

The Magnus effect is a phenomenon in fluid mechanics in which when the rotational angular velocity vector of a rotating object does not coincide with the object's flight velocity vector, a transverse force is generated in the direction perpendicular to the plane composed of the rotational angular velocity vector and the translational velocity vector. Bernoulli's principle is essentially the conservation of mechanical energy of a fluid. Namely:

Kinetic energy, gravitational potential energy, pressure potential energy, constant. The most famous corollary is that when the flow is at a constant height, the flow rate is simpler, and the pressure is smaller.

When people drink water, the same applies to the Bernoulli effect. When you raise the cup to your mouth, your mouth gets used to "sucking" the water in the cup. At this time, the chest expands, the pressure of the gas in the lungs and mouth decreases, and the air near the mouth runs towards the mouth.

And the closer to the mouth the air runs, the faster it runs, and the less pressure it puts on the surface of the water. Therefore, for the water surface in the cup, the pressure of the air in the near mouth part is small, and the far part is larger, and under the action of unequal pressure, the water surface of the near mouth part is slightly higher, and flows into the mouth beyond the edge of the cup. (Excerpted from "Story Physics", edited by Liu Renlong, Science Press, 1980 edition, slightly revised).

What is the premise of the Bernoulli effect? () Slap stupid.

a.equal height.

b.Equal branches accompany the speed.

c.Isodensity.

d.Isobaric pressure.

Correct Answer: a