How Do Airplanes Defy Gravity and Fly?

Ever wondered how those colossal metal birds we call airplanes manage to defy gravity and glide effortlessly through the skies? Get ready to unlock the secrets of flight as we unravel the science and engineering marvels that keep these giants airborne. 

Episode Transcript

Hey there, curious minds, welcome to, I Wonder, the show where we explore the questions you've been wondering about. Today's question comes from Samantha, who's 12 years old. Samantha asks how is it that airplanes are so heavy yet they can fly? Great question, Samantha. If you've ever been on a plane or see one close up, you've probably noticed just how massive they are. It seems almost impossible that something so big could get off the ground, but with a little science and a lot of engineering, airplanes can lift off and soar through the sky. Let's explore how it all works.

All right, first let's just talk about how heavy airplanes really are. The average commercial airplane like a Boeing 737, weighs about... Can you guess? 90,000 pounds, when it's empty. That's roughly the weight of 15 elephants. And when you add fuel, luggage and passengers, the weight could reach over 170,000 pounds. So it's true, airplanes are extremely heavy, much heavier than most other vehicles.

But even though they weigh so much, they can lift off the ground and stay in the air thanks to four main forces. Do you know what they are? Lift, gravity, thrust and drag. Let's break down these four forces. First there's gravity, which we all know pulls objects down towards the Earth. This is why heavy things like rocks or cars fall when you drop them For an airplane, gravity pulls it downward, making it want to stay on the ground. To counteract gravity, airplanes need something called lift. Lift is the force that pushes the airplane up into the sky. This force is created by the wings. When the airplane moves forward, air flows over and under the wings in a special way that creates a pressure difference. The shape of an airplane's wings is curved on the top and flatter on the bottom. Because of this shape, known as airfoil, the air on top moves faster than the air below, which creates lower pressure above the wing. This lower pressure lifts the plane upward, allowing it to overcome the force of gravity. Then there's thrust. Thrust is the force that pushes the plane forward. This was created by the airplane's engines, which either use jet propulsion or propellers to push air backward, moving the plane forward. And finally, we have drag. Drag is the resistance or friction that air creates against the plane's body as it moves forward. To keep flying, the plane's engines have to produce enough thrust to overcome the drag, just like you have to pedal harder on a bike when you're going against the wind. When these forces are balanced correctly lift counteracting gravity, and thrust counteracting drag the airplane can fly.

The shape of an airplane's wings is key to creating lift. Wings are designed to manipulate air pressure around them as the plane moves forward. Air hits the wing and splits into two parts. One part flows over the top and the other flows beneath. Because the top surface of the wing is curved, the air has to travel a longer distance over it, so it speeds up. The faster moving air on the top creates lower pressure, while the slower moving air below the wing creates higher pressure. This difference in air below the wing creates higher pressure. This difference in pressure pushes the wing and the airplane upward. This process, called the Bernoulli principle, is named after Swiss scientist and mathematician Daniel Bernoulli, who discovered that fasterving air has lower pressure. It's this principle that allows the wings to create enough lift to support the airplane's weight.

Creating lift is only possible if the plane has enough forward movement, which is where the thrust comes in. Thrust is produced by the plane's engines, which work by pushing large amounts of air backward. Jet engines, for instance, suck in air, compress it, mix it with fuel and ignite it. This combustion pushes the air out the back of the engine at a high speed, which creates a forward push on the plane. This principle is known as Newton's third law of motion, which says that for every action come on, you know it there is an equal and opposite reaction. Ha ha, yeah. By pushing air backward, the engines create an opposite reaction that pushes the plane forward, allowing it to gather enough speed to generate lift.

So why don't airplanes fall even though they're so heavy? The key is that lift doesn't need to be greater than the airplane's weight to keep it in the air. It only has to match it. Let me say that again. Lift doesn't need to be greater than the airplane's weight to keep it in the air. It only has to match it. As long as the lift generated by the wings is equal to the weight of the airplane, it will stay in the air. In fact, when a plane is cruising at a steady altitude, the lift and weight are perfectly balanced. But what if something changes like the speed of the plane? Something changes like the speed of the plane. If an airplane starts to slow down, there's less air moving over the wings, which reduces lift. That's why planes need to keep a certain speed to maintain flight If the lift drops too low the plane's speed, altitude and angle to make sure that the lift is always strong enough to keep the plane in the sky.

Airplane wings were inspired by birds. Just like a bird's wings, airplane wings are shaped to help airflow in a way that creates lift. Birds tilt their wings and adjust their feathers to change the amount of lift they need, which allows them to glide, soar or dive. Engineers use these principles to design airplanes, creating wings with a shape that produces lift when the plane moves forward. Interestingly, when airplanes were first invented, they were tiny compared to modern planes and didn't carry much weight, but as engineers developed better engines and more efficient wings, airplanes were able to grow larger and carry heavier loads. Today's airplanes can carry hundreds of passengers, along with luggage, cargo and fuel, all thanks to carefully engineered wings and powerful engines.

Here's an interesting fact. Airplanes actually rely on the density of the air around them. At higher altitudes, the air is thinner, meaning there's less of it. This makes it harder for the wings to create lift, which is why planes need to fly at the right altitude where there's enough air density to support their weight. When airplanes climb to high cruising altitudes, they're moving at higher speeds to make sure there's still enough air moving over the wings to create lift.

Another cool fact. Because of the weight of fuel, planes are actually heavier at the beginning of a flight than at the end. As they burn fuel, they get lighter, which slightly changes the balance of forces, making it easier to keep the plane steady in the sky.

So, to answer Samantha's question, airplanes can fly even though they're so heavy because of the way their wings create lift, which counters the force of gravity pulling them down. The engines provide thrust, moving the plane forward and allowing air to flow over the wings, creating the lift needed to keep the plane up. When lift balances out gravity and thrust balances out drag, the airplane can soar through the sky carrying tons of weight, passengers and cargo with ease.

Thanks again to Samantha for such an uplifting question and remember, if you have a question you're curious about, visit us at iWonderPodcastcom and we might just feature it in our next episode of iWonder. Until next time, stay curious and keep wondering.