I love this book. It is a must have for every child. When Nathan was in Elementary School he drove his teachers crazy with all the paper airplanes he was making and flying through the classroom. Now I am on a mission to teach my students to do the same to their teachers!
Paper Airplanes 101
The four forces of flight
The four forces of flight are lift, drag, thrust, and weight.
Lift is the upward force created by the wings moving through the air that sustains the airplane in flight. Lift operates to overcome weight. It must be equal to or greater than the weight of the object in flight and acting in the opposite direction. Lift can be increased by increasing the forward speed of the aircraft or by increasing the angle of attack
Drag is the resistance of the airplane to forward motion. It is directly opposed to thrust and is caused by the resistance of air.
In Lab we built a pencil hellicopter
- A Pencil with an eraser on the end
- A Manila Folder or other card type paper
- A Thumb Tack
Mark the center of the strip with a pencil.
Carefully poke a thumbtack through the center of the strip and into the center of eraser.
Next we Made Catapults
There are many different kinds of ancient catapults. The three major types are the Ballista, Onager and Trebuchet.
The Trebuchet is probably the oldest type of catapult. It was invented either by the Chinese or in the middle east. If you look at an Egyptian shadouf, it looks very much like a trebuchet, and it's easy to imagine that the trebuchet was inspired by the shadouf. Shadoufs have been around since the beginning of recorded history.
A shadouf is just a long pole balanced in the middle, with a weight on one end and a rope attached to the other end with a bucket tied to it. It's easier to pull something down that to lift it up, so people use these shadoufs to lift water from irrigation trenches. (They pull the rope down, and the counterweight pulls the bucket full of water up.) If someone had slipped and let go of the rope, an empty bucket could be flung high and far by the counterweight. A clever perrson might see the weapons potential in this.
Trebuchets were used mainly as lobbing machines to spread fire and diseased corpses, as well as a lot of solid missiles, over the walls of castles to rain down on the inhabitants. They were very effective!
The next oldest type of catapult is the Ballista. This machine was deliberately invented by the Greeks, around 800 BCE. Ballistae were even mounted on warships and used to hurl fire onto other ships.
The Romans took the ballista, used it, and then improved in in the Roman way to create the Scorpion, and then the Onager. Not much is known about how these machines really looked, but our best guess is something like this one.
Onagers were used right up to the middle ages alongside the Trebuchet, when gunpowder and the Cannon were invented and eventually replaced the catapults.