Would You Like to Fly Imagine being an aircraft pilot You could pilot an airplane or the latest stealth fighter Or perhaps you could fly a microlight These tiny aircraft have no cockpit and you fly in the open air Best of all would be to have your very own wings 씱 Swiss inventor Yves Rossy’s jet-powered wings are the closest any human has come to flying like a bird In this book you will learn about the science secrets behind flight What were the first creatures to fly even before birds How can a plane fly upside down What is the fastest plane What about the slowest And what will flight be like in the future 4 This book answers these and lots of other questions You can also do some flight investigations of your own But sadly you won’t get to fly like a bird
2 1 3 4 쑼 One advantage of flight is that it allows animals to travel farther and faster Canada geese migrate thousands of miles each year SUPPORT FROM THE AIR We can barely feel the air so how can it hold up a plane This experiment shows how air can support weight You will need a small plastic action figure tissue paper scissors cotton thread tape 1 Stand on a chair and drop the toy Does it fall quickly or slowly 2 Cut two circles of tissue 6 inches 15 cm and 12 in 30 cm across Fold each into quarters snip off the point then unfold again Stick four short lengths of cotton to each circle one at each crease 3 Tape the small parachute to your toy Drop the figure again Does it fall faster or more slowly 4 Now try the bigger parachute How fast does it fall this time 5
What Keeps Us on the Ground Like other land animals humans can’t really get off the ground We can jump into the air but we quickly get pulled down again There is a force that is always pulling us toward the Earth This force is gravity Birds bats and insects are pulled down by gravity too but they have found ways to counteract this pull Lift Thrust Drag 쑿 The main forces on an aircraft As well as gravity and lift there is thrust provided by the engines and drag air resistance How Does Gravity Work Gravity is a force that attracts all objects toward each other The heavier something is the more mass it has the stronger its gravitational pull On the Earth’s surface the strongest 6 Gravity gravitational pull is from the Earth itself Its gravity pulls everything toward it Large heavy objects are pulled toward the Earth more strongly than small light ones So flying animals and aircraft are designed to be as light as possible This means they need less force to get off the ground
The lighter an aircraft is the less power it needs to overcome gravity and fly Composites and alloys COMPOSITES AND ALLOYS are light strong materials used in advanced aircraft Composites mix materials to get the best of both worlds Carbon composites combine light strong carbon with tough plastic resin They make excellent high performance wings Alloys are metal mixtures One of the lightest alloys a mixture of aluminium and lithium is used in the space shuttle Superalloys are metal mixtures that work well at high temperatures Nickel superalloys are used to make jet engine parts Overcoming Gravity When a bird or a plane flies it has to cancel out the downward force of gravity with an opposite upward force called lift Lift is created when air rushes over the wings of a bird or a plane In level flight the upward lift exactly matches the downward force of gravity 씰 Birds are much lighter than land animals of the same size A golden eagle weighs only about 8 8 pounds 4 kg 7
