Airplanes

Aerodynamic Forces

Before we dive into how wings keep airplanes up in the air, it's important that we take a look at four basic aerodynamic forces: lift, weight, thrust and drag.

A- Lift , B- Thrust C-Weight D- Drag.

Straight and Level Flight
In order for an airplane to fly straight and level, the following relationships must be tr ue:

Thrust = Drag

Lift = Weight

Four forces act on a plane in flight. When the plane flies horizontally, lift from the wings exactly balances the plane's weight. But the other two forces do not balance: the thrust from the engines pushing forward always exceeds the drag (air resistance) pulling the plane back. That's why the plane moves through the air.

You might think engines are the key to making a plane fly, but you'd be wrong. Things can fly quite happily without engines, as gliders (planes with no engines), paper planes, and indeed gliding birds readily show us.

If you're trying to understand how planes fly, you need to be clear about the difference between the engines and the wings and the different jobs they do. A plane's engines are designed to move it forward at high speed. That makes air flow rapidly over the wings, which throw the air down toward the ground, generating an upward force called lift that overcomes the plane's weight and holds it in the sky. So it's the engines that move a plane forward, while the wings move it upward.

Not surprisingly, the bigger the wings, the more lift they create. That's why gigantic planes need gigantic wings. But small wings can also produce a great deal of lift if they move fast enough. Helicopters produce a huge amount of lift by spinning their rotor blades (essentially thin wings that spin in a circle) very quickly.

Explorers

Why did Europeans explore the world during the Age of Exploration?

	To find a sea route to the spices of Asia
	To find gold, silver, and precious stones
	To expand their knowledge of the world
	To control a larger empire
	To expand Christianity
	To find animal furs

In the 1300s A.D. trade had become more costly, and more difficult due to the barbaric Turkish empire. The European nations began to look at other ways of transporting spices into Western Europe. Many adventurous businessmen began to look at the sea.

Prince Henry, the Navigator.

Driven by a desire to find an overseas route to India, Prince Henry The Navigator brought together mapmakers, astronomers, and mathematicians to study star charts, and to help improve methods of ocean navigation. By the late 1400s A.D. Explorers from Portugal had discovered new islands, rivers, trading posts, and even a way to travel from Portugal to India over water.

Bartholomeu Dias

In 1487 a young adventurous explorer by the name of Bartholomeu Dias arrived at the southern tip of Africa, which was later named The Cape of Good Hope. Dias’ bravery helped prove that is was possible to reach Asia by sailing around the tip of Africa.

Vasco Da Gama

Vasco da Gama left Portugal in 1497 hoping to sail around Africa, and reach India. Ten months later, he and his men arrived in Calicut, India. He was the first person to take the sea route and successfully reach India. Vasco Da Gama and his men returned to Portugal as heroes

Christopher Columbus

Christopher Columbus proposed finding a new route by sailing West. Columbus thought that if they sailed West, they would eventually circle the globe, and arrive in Eastern Asia. King Ferdinand, and Queen Isabella of Spain granted him the supplies, men, and ships that he needed to carry out his expedition. Columbus was given three sailing ships named the Nina, the Pinta, and the Santa Maria.

Columbus’ men were terrified that they would be lost at sea, and that they would suffer starvation. As the days wore on, these men began to turn against him. Columbus was forced to agree to turn back, if they did not find land within three days.

On the night of the second day, just before he would have had to turn around, land was sighted. Columbus and his men discovered an island in the Caribbean. Columbus did not realize that he had arrived in a new part of the world. He was convinced that he was in India. For this reason, he called the natives who lived on these islands the Indians.

Columbus returned to the Americas three more times. Each time believing that he was in India. During his life, he never realized what he had discovered.

Amerigo Vespucci

Amerigo Vespucci was an Italian explorer who first suggested that the land found by Columbus was actually not India, but a new world altogether. Because he was the first to realize that a new world had been discovered, map makers began calling this new land the ‘Americas’ in honor of him.

Ferdinand Magellan

Magellan was the first explorer to sail around the entire globe. They proved once and for all that what Columbus had discovered was indeed a new world. They also discovered just how large the Earth really was.

Hernan Cortez

Conquered and devastated the Aztec Empire in Mexico, and set himself as the ruler of Mexico, on behalf of Spain.

Francisco Pizarro

Francisco Pizarro discovered another wealthy empire in Peru known as the Inca Empire. Pizarro was able to capture the Incan King, Atahualpa, and hold him ransom. After the Incas paid Pizarro a ransom for the release of their leader, Pizarro had Atahualpa put to death, along with other top leaders in the Incan Government. The result was that the Incan Empire also fell.

Plymouth

A group of poor farmers in England, called the pilgrims, settled a new colony in the Americas, called Plymouth. They made their journey on a ship named Mayflower.

Plants and Pollination

History: The very earliest photosynthesizing plants on Earth had only one cell, and they reproduced by mitosis: splitting themselves in half.

By about two billion years ago, some of these cells began to split themselves in a more sophisticated way, called meiosis, where there's a daddy cell and a mommy cell and each parent cell makes a new cell with a copy of half of its DNA. With all this mixing up of DNA, plants began to evolve much faster than they had before. Soon there were plants with more than one cell, likeseaweed

When the first plants like moss began to live on land ago, they developed a way to reproduce using spores instead.

Spores worked well for the moss, and also for the ferns that evolved later on. But these spores counted on falling on to wet ground; if they didn't find wet ground they just died.

When plants began to spread on far from the edges of streams, they needed a way to protect baby cells that fell on dry land. That's when the earliest plants gradually evolved hard covers for their baby cells, or seeds. Soon, there lots of seed plants, mainly pine trees, all over the land.

Beginning around the same time, a few plants were developing new ways to help out their reproduction: flowers, and fruit. Flowering plants needed bees to land on them and carry theirpollen from flower to flower. Bees and flowers evolved together, and they are symbiotic - bees can't live without flowers, and flowers can't live without bees. The earliest flowers developed as a way to attract insects and get them to help spread the plant's pollen far away from where the plant was growing.

Many plants, such as grass, weeds and even large pine trees, rely on the wind for pollination. The pollen is small and light, allowing it to be blown by the wind. The pollen lands on other plants and fertilizes them.

Why will a seed die if it grows directly under its parent?

Class Apart Quiz - Apr 29th, 2010

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