FOUR FORCES OF FLIGHT
Today we will learn about the the four forces of flight and how aircraft move!
Before we start, let’s reflect on these questions:
What are the four forces of flight?
The four forces of flight are gravity, lift, thrust, and drag.
Gravity is the force that pulls all things toward the center of the Earth.
Lift is the upward-acting force on an airfoil.
Thrust is a force that pushes something forward.
Drag is the resistance offered by a fluid, like air or water.
Collection of the Intrepid Museum. Gift of the family of Forrest Masters. P2021.29.05
How do the forces of flight act on a moving object?
Drag acts opposite to the direction of motion. As a bird moves forward, for example, it will face drag from the air around it. Drag is caused by friction and changing air pressure.
Gravity pulls all things toward the center of the Earth. It acts in a downward direction on all objects. It creates weight.
Collection of the Intrepid Museum. Gift of Robert and Sue Ann Dilts. P2011.48.27
How do the forces of flight act on a moving object?
Lift and thrust work against drag and gravity to move a vehicle through the air.
Lift is created when the pressure on top of an airfoil is less than the pressure below the airfoil. It is the force that holds an aircraft in the air.
Thrust moves an object in the direction of motion. When air is moved in one direction, the object is moved in the opposite direction.
Let’s Visit Intrepid!
Press play on the next slide to travel to the Intrepid Sea, Air & Space Museum and learn how the four forces of flight affect aircraft and spacecraft.
How does the design of an aircraft help it fly?
An aircraft or spacecraft must move air in order to create thrust. They may use a propeller, jet engine, or rocket. Air is pulled in and then pushed out in an opposite direction.
Collection of the Intrepid Museum. Gift of Robert and Sue Ann Dilts. P2013.30.08
How does the design of an aircraft help it fly?
To create lift, airplane wings and helicopter propellers are in the shape of an airfoil.
When air moves over an airfoil, it builds up more pressure on the bottom than on the top. The greater pressure on the bottom allows the airfoil to lift into the air, and the vehicle to fly.
Collection of the Intrepid Museum. Gift of Robert Wayne Osburn and family. P2013.149.18
Let’s Explore: Gravity
What happens when you drop a pencil off your desk? Where does it go? Why?
Let’s Explore: Lift
Lift is created by air moving on the top and bottom of an airfoil. Airfoils are not always the exact same shape. The image on the right illustrates the “family of airfoils,” as described by the National Advisory Committee for Aeronautics in 1929. Describe the shapes that you see!
NASA
Let’s Explore: Lift
Which of the following are examples of airfoils?
A Bird’s Wing
National Archives
Wing of the TBF-1C Avenger
Collection of the Intrepid Museum
Helicopter Rotors
Department of Defense
Answer: All of them!
Let’s Explore: Drag
Rub your hands together as fast as you can. What happens?
The heat you feel is a result of friction.
The same thing happens when an airplane moves through the air. The friction between the airplane and the air is called drag.
Collection of the Intrepid Museum
Let’s Explore: Drag
Have you ever stuck your hand out the window of a moving car? What does it feel like?
Collection of the Intrepid Museum
Let’s Explore: Drag
Can you think of a situation where drag would be useful?
Hint: think about safety in the skies.
Collection of the Intrepid Museum
Let’s Explore: Thrust
When designing aircraft and spacecraft, engineers must consider thrust. Thrust moves a vehicle forward and works against drag. Some examples of ways that vehicles create thrust are:
Propellers!
Collection of the Intrepid Museum
Jet Engines!
NASA
Rockets!
NASA
Let’s Explore: Thrust
Look at the photos below and share how each vehicle creates thrust.
Collection of the Intrepid Museum
NASA
Collection of the Intrepid Museum
Propeller! Rocket! Jet Engine!
Let’s Make a Kite!
A kite is a flying machine you can make by hand. Using one exemplifies the forces of thrust, lift, gravity, and drag.
Use visual instructions to fold and put together your kite.
Fly the kite in a place with moving air - like outside!
Watch what happens!
Let’s Make a Kite!
Cut copy paper into a square (8.5 inches by 8.5 inches). Optional – decorate one side of paper or use paper with images printed on one side.
Fold the square in half along the center diagonal line. Fold so that the blank side of the paper is inside, and the color side is visible.
Let’s Make a Kite!
Now take one edge and make a fold to the centerline as shown. Turn the paper and repeat this step for the other side.
Fold the small corner to the center line. Repeat it for the other side as well.
Let’s Make a Kite!
Use some tape to strengthen the small triangle flaps and end point as seen below.
Use a hole punch or scissors to make holes where you placed tape.
Let’s Make a Kite!
Cut two 9 inch strings and one 7 foot string. You'll tie the shorter strings to the two holes on the small triangle flaps. Then tie the other ends of the shorter strings together in the middle.
Now, let's make the tail! Cut a piece of streamer and twist one end. Attach it to the end point at the back of the kite (where you punched a hole before)
Let’s Make a Kite!
Make the winder by tying one end of the 7 foot string to the center of the craft stick. Tie the other end of the string to the knot joining the 9 inch strings on the kite. Wind the rest of the string around the craft stick.
Enjoy your kite! It doesn’t take much wind to fly, but make sure you have moving air!
Reflection