Gravity's Strength and Centrifugal Force: Exploring the Laws of Physics

[Lucky Eddie]

I've a question about Gravity that's been bugging me...

I understand (maybe incorrectly - please feel free to correct me if I am wrong) that gravity acts equally on all masses at all points on the globe.

At the same time - the Earth spinning about its own axis creates a centrifugal force that tries to fling us all off the globe - but that gravity is some 350 times stronger than the centrifugal force, thus we stick to the Earth because of the stronger force of gravity like a fly sticks to fly paper.

So why is gravity sometimes called the "weak force" of the universe?

I mean if you tie a metal nut to a piece of string and whirl it around your head you will soon come to realize, that centrifugal force is quite strong - whirl that nut on the string in a vertical plane and let it go on the upward arc and it will beat gravity easily and go straight up much like a rocket and possibly even out of sight before it eventually comes back down much like a bullet or arrow fired upwards into the air.

BUT - if we could twirl it around in a vertical orbit fast enough - or with a long enough diameter length string or a heavy enough mass - might we not generate enough force to let the nut actually leave the Earth's atmosphere and effectively launch it into space?

So I am saying is it not possible to generate enough centrifugal force to overcome Gravity?

I weigh a lot more than a metal nut - let's say 120 kilos (about 250 pounds, yeah I know - Fatty Arbuckle's got nuthin' on me)... ;o)

Also - standing on the Earth's surface, at the radius of the Earth's circumference here on the Earth's crust, my "piece of string" orbital distance from the center of the Earth is way longer than the string twirling the metal nut around my head in a vertical plane to shoot it up into the air when I let go the end of the string.

We know that the Earth spins about its own axis once every 24 hours, so that effectively we are actually traveling very fast in MPH (meters per second) terms, so the centrifugal force created should be huge compared to say the little nut on a string in the earlier example.

So for me not to fly off out into space - Gravity holding me down must be way in excess of the centrifugal force generated with so much mass at such a long orbital distance from the center of the Earth at the Earth's crust traveling at such a high speed around the Earth's axis.

So why does the iddy biddy little nut travel so high in the air with such little speed and mass when I let go the string on an upward arc - defying the force of gravity for a long time - yet I, who weigh much more and travel much faster and have a much longer piece of string distance, stay firmly planted here and not fly off out into space?

The usual answer is that "weak ol gravity" is much stronger or more than centrifugal force and that's why I stay put.

More to the point...

At the equator, I am at the furthest distance to the Earth's vertical axis of spin - in terms of my "length of string" distance for generating centrifugal force.

As I move north or south of the equator my "length of string distance" to the Earth's vertical axis of spin, for creating this centrifugal force shortens just as the lines of latitude around the Earth also shorten as we move north or south of the equator.

So by my 'calculations' in my head - if my weight is the difference between the gravity holding me down minus the centrifugal force wanting to throw me off the planet - then as I move north of south of the equator and my string length distance to the axis of spin decreases then my centrifugal force should lessen as I get toward either of the two poles of the planet and thus I should weigh MORE.

Thus - if I do really want to lose weight in a hurry - all I have to do is move towards the equator where I will weigh the least - due to increased centrifugal force due to increased string length from the center of axis of spin...this increased centrifugal force and reduced result of interaction of gravity and centrifugal force makes me weigh less.

If I go towards the poles I thus get heavier?.

No more diets - just walk (drive / fly) north or south towards the equator depending where I am, to weigh myself?

Yippee Mars bars for everyone without any calories guilt. ;o)

This can be the new "Hollyweird" diet fad of the century, maybe I can sell it on TV and retire comfortably on the proceeds?.

So...where exactly did I go wrong please, dieting can't be this simple can it?

Anyone?

 

[mathman]

Gravity is called weak in comparison to the other three fundamental forces. Example: a toy magnet can lift a paper clip, even though the gravity of the entire Earth is trying to hold it down.