Flight lesson 1 · Grades K-5
How Things Fly
Birds, bees, kites and paper airplanes all use the same four pushes and pulls!
Hi, I'm Amelia! Look up. Do you see a bird, a plane or a kite?
Today we will find out what keeps them up in the sky. Let's take off!
The four forces of flight
A force is a push or a pull. Four forces work on everything that flies. Some push it up or forward. Some pull it down or slow it down.
Lift: up!
Lift pushes a flier up. Wings, spinning blades and hot air can all make lift.
Weight: down!
Weight pulls a flier down. It comes from gravity, which pulls everything toward the ground.
Thrust: go!
Thrust pushes a flier forward. A propeller, a jet engine, flapping wings or your throw can make thrust.
Drag: slow down!
Drag is the air pushing back. It slows a flier down. Smooth, thin shapes make less drag.
To go up, a flier needs more lift than weight. To speed up, it needs more thrust than drag.
How a wing makes lift
Air is made of tiny bits you cannot see. When a wing moves through the air, it is tilted up a little at the front. Its shape and its tilt push the air down.
When you push on something, it pushes back on you. So the air pushes the wing up. That push is lift!
The top and the bottom of the wing both help. Air flows faster over the top, and the air there pushes down on the wing less. The air underneath pushes up more.
A wing needs two things: air and moving. No air, no lift. That is why wings do not work in space! No moving, no lift. A plane must zoom down the runway before it can fly.
Try it: your hand is a wing
In the bath, hold your hand flat and slide it through the water. Now tilt the front of your hand up a tiny bit. Can you feel the water push your hand up? Water and air both push back like this.
Birds and bees
Birds flap and glide
Birds use the same four forces as planes. A bird's wing is shaped like a plane's wing, so a bird can glide.
When a bird flaps, its wings push on the air. The air pushes the bird up and forward. So one flap makes both lift and thrust! On the way back up, the bird bends its wings a little so they do not push the air as much.
Insects flap super fast
Insects flap their wings too. A honeybee's wings are tiny, so it flaps them very, very fast.
Wow! A honeybee flaps its wings about 230 times every second.
Bees do not just flap up and down. They twist and swish their wings in tricky ways to stay in the air.
Kites
A kite has no engine. So how does it fly? The wind does the moving for it!
Wind flows over the tilted kite and makes lift. Weight pulls the kite down, and drag pushes it back with the wind.
The string is the secret. It pulls against the wind. That pull does the job thrust does on a plane. If the string breaks, the kite drifts away with the wind and falls.
The Wright brothers flew their gliders as kites to learn how to fly. Kites are great teachers!
Paper airplanes
A paper airplane uses all four forces too:
- Thrust comes from your throw.
- Lift comes from its flat wings pushing air down.
- Weight pulls it down to the floor.
- Drag slows it down.
After your throw, there is no more thrust. The plane glides until drag slows it and it lands.
Here is a fun fact: paper airplane wings are flat on top and on the bottom, and they still fly! That shows a wing does not need a curved top. It needs a little tilt to push air down.
Try it: be a flight tester
- Fold a paper airplane. Ask a grown-up if you need help.
- Throw it gently three times. Count how many steps it flies.
- Now change one thing. Fold the wings wider, or bend the back edges up a tiny bit.
- Throw it three more times. Did it fly farther or shorter? Why do you think so?
Scientists change one thing at a time. That is called a fair test!
Planes, helicopters and hot-air balloons
Planes
A plane's wings do not flap. Instead, the whole plane moves forward fast. A small plane gets thrust from a spinning propeller. A big jet gets thrust from jet engines. Then the wings make lift.
Helicopters
A helicopter's long rotor blades are spinning wings. They spin around and around and make lift. A helicopter can go straight up, stay still in the air, and even fly backward or sideways!
Hot-air balloons
A balloon has no wings at all. A burner heats the air inside it. Hot air is lighter than the cool air around it, so the hot air rises and lifts the balloon up. To come down, the pilot lets some hot air out of a vent at the top.
The Wright brothers: the first airplane flight
Wilbur and Orville Wright were brothers. They started studying flying in 1899. They tested kites and built three gliders.
Then they built a plane with an engine, called the Wright Flyer. On December 17, 1903, near Kitty Hawk, North Carolina, Orville flew it for 12 seconds. He went 120 feet. It was the first time a person flew an airplane with an engine!
They took turns and flew four times that day. Wilbur flew the longest flight: 852 feet in 59 seconds.
The real Wright Flyer now belongs to the Smithsonian's National Air and Space Museum.
Amelia Earhart: a brave pilot
Amelia Earhart was a famous American pilot. In 1932, she flew all alone across the Atlantic Ocean without stopping. She was the first woman to do it!
She flew a bright red plane that she called her "Little Red Bus." The trip took about 15 hours. Later that year, she became the first woman to fly alone across the whole United States without stopping.
I am named after her. She showed the world that girls and boys can both be pilots!
Game: Force Finder
How to play: press Start. Look at the big yellow arrow and read the clue. Pick the force: Lift, Weight, Thrust or Drag. You can tap or click a button, or press a key: L for lift, W for weight, T for thrust, D for drag. There are 8 rounds.
Press Start to find the forces!
Quiz: are you ready to fly?
Pick one answer for each question. Then press "Check my answers."
For grown-ups
About lift: this page explains lift the way NASA Glenn Research Center does: a wing turns (deflects) the moving air downward, and by Newton's third law the air pushes the wing up. Both surfaces matter, and the pressure difference (lower above, higher below) is the same story told another way. We deliberately avoid the popular "equal transit time" idea, which says air over the curved top must "catch up" with air underneath. NASA Glenn calls that theory incorrect: air over the top actually arrives well before the air below, flat paper-airplane wings make lift, and planes can fly upside down. Some children's books still use it, so if your child brings it up, the paper airplane is a great counterexample.
About kites: on a kite, the string's pull (tension) balances lift, drag and weight; we describe it as "doing the job of thrust," following NASA Glenn's comparison. Safety: fly kites in open spaces far from power lines, and do paper-airplane tests where nobody can be poked.
Words to know: force, lift, weight, gravity, thrust, drag, glide, propeller, rotor, fair test. Ideas for more: compare how far a heavier paper airplane flies, or watch birds flap and glide on a walk.
Sources
Facts on this page were checked against:
- NASA: What Is Aerodynamics? (Grades K-4) (the four forces, propellers and jets, gliders, hot-air balloons, helicopter lift)
- NASA Glenn Research Center: Four Forces on an Airplane (a force is a push or pull; what each force does)
- NASA Glenn: What is Lift? (wings turn the air; no air, no lift; no motion, no lift)
- NASA Glenn: Incorrect Lift Theory, "Equal Transit" (why the equal transit idea is wrong; flat paper-airplane wings)
- NASA Glenn: Forces on a Kite (the string's pull, and the Wrights' kite tests from 1900 to 1902)
- Smithsonian National Air and Space Museum, How Things Fly: How do birds fly? (flapping makes lift and thrust; bending wings on the upstroke)
- Smithsonian How Things Fly: How do bees fly? (about 230 wing beats a second)
- NASA: What Is a Helicopter? (Grades K-4) (rotor blades; hovering and flying backward or sideways)
- Smithsonian How Things Fly: How does a hot air balloon fly? (hot air is lighter than cool air; the burner; letting air out of the top vent to come down)
- Smithsonian National Air and Space Museum: 1903 Wright Flyer (December 17, 1903; 12 seconds and 120 feet with Orville; Wilbur's 852 feet in 59 seconds; three gliders first)
- Smithsonian National Air and Space Museum: Amelia Earhart and Lockheed Vega 5B, Amelia Earhart (1932 solo nonstop Atlantic and U.S. flights; the "Little Red Bus"; about 15 hours)
Credits: Words, drawings, game and quiz by Amelia for the Jugami School Elementary Science Department. All art is original, hand-made SVG; the pictures of the Wright Flyer and of Amelia are friendly cartoons, not exact copies. No ads and no tracking. Your game and quiz answers stay on this page.