By Ida Shim (Y10)
Over the past decades, airplane has increasingly become a popular method of transportation. The familiar rush of takeoff with the roar of engines is both exciting and somewhat unsettling. After all, how can a machine weighing hundred of tonnes rise gracefully into the sky? Why doesn’t it simply fall back to Earth?
The Four Forces That Make Airplanes Fly
There are four forces that control every airplane in the sky.
Weight is the force of gravity that pulls the plane down, lift is the force that goes up and counteracts gravity, thrust is the force that goes forward and is made by the engines, and drag is the force of the air that pushes back
For an airplane to fly smoothly, lift has to balance weight and thrust has to balance drag. These forces are always working together, changing as the plane goes up flies straight or comes down.
Gravity is always pulling the airplane towards the earth. but airplanes can fly because they are designed to make lift, which is a force that is strong enough to overcome the pull of gravity.
How Do Wings Make Lift?
The secret to lift is in the shape of the airplanes wings.
Most airplanes have wings that are curved on top and flat on the bottom. When the airplane moves forward, the air flows over and under the wing. Because the top of the wing is curved, the air moves over the top than under the wing.
This means that the air pressure is lower on top of the wing and higher on the bottom, according to Bernoulli’s principle, where faster moving air exerts lower pressure. This difference in pressure makes the wing go up which is called lift.
But that’s not all; the wing is a bit tilted up so it pushes the air down. When the wing pushes the air down the air pushes the wing up with an equal force, following Newton’s Third Law of Motion(for every action, there is an equal and opposite reaction).
Together, pressure differences and air deflection create enough upward force to lift an aircraft into the sky.
Engines: Producing Thrust
Lift alone is not enough to make an airplane fly. The airplane also has to move very fast so that the air can flow over its wings.
Modern airplanes, like the ones made by Boeing and Airbus, use powerful engines to make thrust. These engines suck in air, compress it, mix it with fuel, and ignite it. The hot gases rush out the back at high speed.
Again, Newton’s Third Law applies; as gases are expelled backward, the plane is pushed forward.
The faster the plane moves, the more lift the wings can make. That is why airplanes go fast before they take off, as they have to reach a certain speed to make enough lift.
Why Do Airplanes Stay in the Air?
When an airplane is flying, it has to balance all the forces.
At cruising altitude(around 10-11 km), the air is thinner. This means that there is less lift but there is also less drag, and allows the airplane to fly fast(800-900 km/h for commercial jets) using less energy.
The engines provide continuous thrust to counteract drag. while the wings keep making lift to counteract the weight of the airplane. If the lift is more than the weight the airplane goes up(climbs), and if the weight is more than the lift it goes down(descends).
What Happens When There is Turbulence?
In most cases, turbulence is simply irregular movement of air.
Airplanes are designed with flexible wings that can bend significantly without breaking. They are also tested to make sure they can fly safely even in extreme weather.
The physics of flying is still the same even when there is turbulence. The lift is still counteracting the weight, thus the airplane won’t fall down.
Energy in Flight
Another important concept about flight is how energy changes.
When an airplane takes off and climbs, its engines convert the chemical energy from fuel into kinetic energy and gravitational potential energy. When it descends, some of that energy converts back into movement.
The physics of energy states that energy does not disappear, but rather changes form and remains conserved.
Human flight once seemed impossible, but it is now made possible by applying Newton’s laws and principles of fluid dynamics. Every time an airplane takes off, it is not defying gravity but deliberately balancing lift, weight, thrust, and drag. As shown, what feels like impossible could be simply done by physics working exactly as it should, as long as we are able to use it for us, not against us.
- NLCS Jeju
