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Politics : Formerly About Advanced Micro Devices
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To: J_F_Shepard who wrote (749322)10/25/2013 1:51:48 PM
From: TideGlider1 Recommendation

Recommended By
Bill

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You don't realize how fast the blades are moving because they are so large. The speed and mass of the blades is great enough to kill and earthly animal that it contacts. They appear at times as you could simply take hold of the blade and go for a ride.

The speeds along the blade are variable.

There are two different speeds to consider in this issue. The first is linear speed. Linear speed describes a length divided by a time, such as running a 100 meter dash in 12 seconds. This is your speed in regards to the distance that you travel over a period of time. However, when traveling in circular motion, you will also have what is called angular speed, the second type of speed. Angular speed is measured in units of degrees/ second or radians/ second, and describes an angle divided by a time.

For example, to examine your scenario in which a turbine spins at 120 mph, the units of miles/ hour indicate a linear speed (distance/ time) and therefore this speed will not be same for all points on the blade. Why?

speed = distance / time
speed = circumference / time period
speed = (2 x pi x radius) / time period

As you can see, points with different radii along the blade will trace out different circumferences in the same time period. Therefore they cannot have the same linear speed because they are traveling different distances (different circumferences, depending on radius from center). I would assume that 120 mph corresponds to either an average point or the blade tips, as it will vary along the length of the blade.

However, because the blade is rigidly connected as you pointed out, every point along the blade will have the same angular speed as they all trace out the same angle within any given time period.

All that to say:
Linear speed - varies along the blade length
Angular speed - constant along the blade length
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