Re: Earth kinetic energy -- correction


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Message 1257 from Kirk McLoren, 07 February 2004 23:50:

In response to message 1256: Re: Earth kinetic energy from Kirk McLoren , 06 February 2004:

I got corrected by a nice person on the high voltage list.4hv.org Thanks again James--

A 'pound' is not a unit of mass. To calculate kinetic energy with English units you need to express the object's mass in slugs -

In the English system the unit of force is the pound-force, the unit of length is the foot and the unit of time is the second. Masses experience an acceleration of 32 ft/s under gravity.

The amount of 'unit mass' that experiences a foot-pound of force is found from-

F = ma => m = F/a => 1/32 unit mass

In other words, if you hold a mass in your hand that weights 1 pound-force then you are holding 1/32 of a slug. If 1 pound-force is applied to a mass of 1 slug then it will accelerate at a rate of 1 ft/s2 (this is how a slug is defined), in the same way that a mass of 1 kg will accelerate at a rate of 1 m/s2 under the application of a force of 1 newton.


Looking at the example again with appropriate units -

Potential Energy of 1 pound-mass (a mass that weights 1 pound-force) raised by 16 foot -

Ep = F x h
= 1 x 16 = 16 foot-pounds

Kinetic energy of 1 pound-mass (1/32 of a slug) after falling 16 feet -

Ek = 0.5 x m x V2
= 0.5 x (1/32) x 322 = 16 foot-pounds


> > > to get the kinetic energy you will need this formula ke=1/2mv^2 then i have calculated that the total earth's kinetic energy by spinning is 4.8x10^29 joules if we can think of a way to tap the earth's kinetic energy then that would surely solve our problem of electricity shortage

> Kinetic energy footpound is not an engineering footpound. Consider a 1 pound weight lifted 16 feet. It has a potential energy of 16 footpounds or you can say 16 footpounds was imparted to raise it. We now drop it and 1 second later it hits bottom with a velocity of 32 feet per second. The KE is 1/2 32 squared or 512 "foot pounds" Looks like the basis for a hell of a perpetual motion or free energy machine. LOL. 16 to 512 is a heck of a lot of free lunch. Or maybe not the same "footpound". I'll stick with the second explanation

> As for extracting the energy use a reaction wheel. Draw a wheel suspended above the earth. place a dot on the wheel. Draw the wheel and earth every six hours, dot not moving. To extract energy you would rotate wheel and extract each time you reverse direction of rotation, ie rotate 180 degrees on suspension axis, not rotation axiis. 2 rotations going on here. one on axle , one on mount.
> -Kirk KC7THL




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