You have learned that acceleration is the time rate change of velocity. And as you are presently learning, the acceleration of an object is directly related to the net force on the object. From the large centripetal accelerations to which high speed rotors are subjected to the relatively minute accelerations of a seemingly smooth airplane trip, acceleration is a subject of intense study in many fields of engineering and technology.
Consider the accelerations during a typical trip on a commercial airline. The accelerations during takeoff and landing are quite apparent, as well as those which occur during encounters of air turbulence. But you probably do not notice accelerations during the bulk of the trip. However, for the inertial guidance system on the plane, those long periods of unfelt accelerations are just as crucial to determining the net displacement of the airplane as those higher short-duration accelerations. A tiny change in direction at the first of a thousand mile trip can make a big difference in the net displacement at the end of the trip.
The inertial guidance systems of commercial aircraft depend upon the detection of those subtle changes in direction and speed. The systems presently used by commercial airlines are incredible precision-made mechanical devices utililizing gyroscopes. They are very expensive. The production of a low cost version for use in navigational systems for cars (and for aviation as well) is being pursued at several institutions. The Intelligent Transportation Systems (ITS) is one such project under the direction of PATH Sensor Group at UC Berkeley.
The study of large accelerations is important many areas. Instruments aboard the Space Shuttle must be able to withstand the accelerations and vibrations of takeoff and landing. NASA's HCC Centrifuge at the Goddard Space Flight Center is used for testing equipment under such conditions without the obviously immense expense of testing during an actual launch.
Closer to earth, NASA's Aircraft Landing Dynamics Facility (ALDF) analyzes the stresses on landing gear under a variety of conditions by accelerating a testing platform to high speeds over relatively short distances.
To study how various structures respond to the catastrophic accelerations experienced during earthquakes, the UC Davis Engineering program has a huge centrifuge used for their geotechnical modeling center. The centrifuge has a radius of 9.1 m and can handle a maximum payload mass of 4500 kg. It is the largest geotechnical centrifuge in the world and handle accelerations up to 53g. (Note: Most humans become unconscious when subjected to 6 - 10 g's.)
And finally, there are the
accelerations necessary to quickly separate suspended solids out of
liquids. Centrifugal accelerations are used for large scale water
filtration, such as those produced by Mid-Continental's decanter
centrifugal filtration
pump, a diagram of which is shown. Although these pumps operate at
very high rotational speeds, they pale in comparison to some of those used
in chemistry and biology labs.
Although there are plenty of lower speed centrifuges (around 3200 rpm, for
example) such as those in UVI's chemistry and biology labs, higher speeds
are required for separating minute particle suspensions. Indeed, in some
cases, larger molecules can be separated from smaller ones. As a rough
guide, "high speed" centrifuges include those that spin between 17,000 and
30,000 rpm and those that run above this speed are dubbed
"ultracentrifuges". Check out the
high speed centrifuge overview by Michael Brush of U of Penn. (I've cached a non-graphics version if you have trouble getting to the U of P site.)
May the high g force be with you.
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