Want to "fly over" the traffic jam ahead? This high-tech car can actually fly into the sky! The scientific principle behind it is...

When you are stuck in traffic, you often have this kind of conversation:

"Can the front one go faster?"

"If you have the guts, just fly over there!"

Now, cars that can fly over obstacles really exist!

Recently, the Alef Model A flying car completed a test flight in an urban environment in California.

Without wings and visible propellers, how can a heavy car fly?

It is understood that the flying car is equipped with multiple propellers. The principle is similar to that of a small drone. It adopts an eight-rotor setting and is equipped with 8 electric propellers with a diameter of approximately 61cm . The mesh structure on the car body allows air to pass through the entire body.

It turned out that the propeller was hidden inside the car!

How to achieve “take-off on the spot”?

Why can light air hold up a heavy machine? We can do a small experiment. All we need is a book and a small piece of paper 5 mm square! Put the small piece of paper on the book, hold the book horizontally to the position of the chin, and then blow air slowly in the horizontal direction for a while, making sure that the air flow does not blow directly on the paper, but passes horizontally above the paper. After a while, the paper will "jump" up and fly forward for a distance!

In the experiment, because the air velocity above the paper is high, the air pressure above the paper becomes low, and the pressure difference produces an upward force (greater than the downward force of gravity) that makes the small paper fly! This relationship between fluid velocity and pressure is called the " Bernoulli principle ."

The same principle is reflected in many places. On subway or high-speed rail platforms, there is always a "safety line" drawn next to the track, warning people not to cross it. When a fast-moving train passes by, the air flow rate is too high, resulting in lower air pressure nearby. If you stand too close to the train, the thrust generated by the pressure difference between the front and the back will "push" you towards the train, which is very dangerous!

Helicopters take off using the same principle!

Lift generation: by rotating "big fan"

The huge main rotor on top of the helicopter is like a high-speed rotating "fan". The cross-section of each rotor blade is similar to that of an airplane wing (curved at the top and straight at the bottom). When it rotates, the air above has a fast flow rate and low pressure, while the air below has high pressure, thus generating an upward lift (Bernoulli's principle). When the lift exceeds the weight of the helicopter, the helicopter can take off vertically or hover.

Controlling lift: collective pitch lever

The pilot uses the "collective pitch lever" operated by his left hand to adjust the tilt angle (angle of attack) of all rotor blades at the same time. When the lever is pulled, the blade angle of attack increases, and the lift increases; when the lever is pushed, the lift decreases. At the same time, the engine automatically adjusts the throttle to keep the rotor speed stable.

Counteracting fuselage rotation: the role of the tail rotor

When the main rotor rotates, a reaction force (torque) is generated, causing the fuselage to spin in the opposite direction. The "small fan" (tail rotor) at the tail counteracts this rotation through lateral thrust. The pilot uses pedals to control the thrust of the tail rotor to achieve fuselage stability or steering.

In short, a helicopter generates lift by rotating its main rotor, uses its tail rotor to prevent the fuselage from rotating, and achieves vertical take-off and landing, hovering, and flexible steering by adjusting the blade angle and rotor tilt direction.

In addition to flying cars, what other novel and interesting modes of transportation might there be in the future? Feel free to leave a comment in the comment section!

Review expert: Zhou Jianding, Chairman of Xiaoshan District Science Education Committee, and Director of Xiaoshan District Wenyuan Experimental School of Hangzhou Xuejun Middle School Education Group

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