Description - Polar Peoples by Andrew Haslam
Examining key scientific principles, from the force of gravity and natural flight of birds to man's early inventions, such as boomerangs, bows and arrows and sophisticated flight machines, jet engines and rockets, this book is one of series which promotes learning through being a "scientist". It is intended that children develop their observation skills and create original models which demonstrate physical principles behind the most simple and complex inventions. Photographs of birds have revealed that it is the shape of their wings that made flight possible. The wing shape means that lift is produced as air moves over it. A frisbee spins in the air and it is this which gives it stability. Instructions for the making of a frisbee and a boomerang illustrate that their spinning and their curved shape causes them to change direction when flying. The making of a simple crossbow reveals how the flights at the end of the arrow affect the accuracy of the arrows. If there were no flights the arrow would wobble as it moved through the air and it would not be able to hit targets accurately.
Experiments are made with: a home-made cannon to find out how to make the ball travel further or higher; a kite to demonstrate how, to keep flying, it must be held at an angle against the wind; a parachute which when opened causes air resistance; a hot air balloon filled with hot air is less dense than cold air, so the ballooon rises; airships which are filled with helium float in air because hot air is lighter than cold air; gliders must have rising currents of warm air, called thermals to give them lift. Readers are asked to look at the top surface of an aeroplane wing which is curved, while the bottom surface is flatter. Most wings have this shape called an aerofoil. Air moves around this aerofoil as the plane flies. This provides the lift which keeps the aeroplane in the air. To further the explanation of flight this book describes delta wings, swing-wings, propellers, powered flight, flight control, helicopters, jet engines and rockets.
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