Rock Street, San Francisco

This explanation is also flawed. For example, in this theory the top side of the wing is not considered at all, so therefore any lift calculations made are extremely inaccurate. Also about 100 years after Newton found this, a man named Leonard Euler proved Newton’s theory about air particles acting like shotgun pellets wrong due to the fact that a shot gun fires a minute amount of particles over a relatively wide area in comparison to the millions of air particles that a wing might hit, and the closeness of particles of air. However at hypersonic speeds (over 5 times the speed of sound), and at very low air pressures this theory becomes true, and air particles act more like shotgun pellets.

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RADAR is an acronym for “RAdio Detection And Ranging”. Radar is primarily used for detection of aeroplanes and ships. However, it is also used for weather prediction, using it to detect large rainclouds and storms, information like this is very useful for pilots to know about, as they may have to alter flight paths and schedules accordingly. Radar works by sending out short, high intensity burst of high frequency radio waves. By detcting their echo to return it gives the ability to determine an objects location, distance (range), speed and in some cases, identity. The distance and therefore location are found by the time it takes for the beam to return to the receiver, in early radar machines, this information would then be projected onto a cathode ray tube.

The speed of the object can be determined by the doppler shift of the beam. For example, if the object is coming towards the radar, the beam would have been ‘squashed’ and the wavelegnth decreased and the frequency increased, and if the object was moving away the wave would be ‘stretched’ and the opposite would occur. Doppler shift can be calculated with a simple calculation: Doppler Shift = 2x the Relative speed between reciever and transmitter Wavelength of transmitted signal.

This means that if you know the doppler shift (the amount that a wave has been shifted), by knowing knowing the wavelength of both transmitted and received (shifted) waves you can work out the relative speed of the object. For example, if a radar picked up a doppler shift off an aeroplane of 420, using a radar beam with a 1.2m wavelength, you can multiply these numbers together to get 504. you can then half this to get the speed of the plane, which is 252m/s, which is approximately 567mph, or 907.2 km/h, which is approximately the cruising speed for a Boeing 747 Jumbo Jet

The same principles of Radar are also used in Sonar, and Lidar. Sonar (a sound wave equivilant of radar), has very little use anywhere except underwater, due to the fact that sound waves don’t travel very far in air, and is therefore used mainly on ships and submarines. Lidar, (a light wave equivilant) which is being used in parts of the world by police as a replacement for speed radars.

Bibliography

Images http://www.shorehamairport.co.uk/ Self Drawn http://www.yesmag.bc.ca/focus/flight/flight_science.html Self Drawn