# Naked Science Forum

## Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: neilep on 27/01/2006 21:53:34

Title: You spin me right round baby right round !!
Post by: neilep on 27/01/2006 21:53:34
Oh gawwwd !!..Celebrity Big Brother..NO NO NO !!

As I figure, the Earth spins around pretty fast eh ? a few hundred miles per hour yes ?...

well...when I escape the family in the middle of the night I hide myself away and find myself on rounbdabouts which also spin !!..

....how come I can feel the spin of the roundabout and not of the Earth which is spinning a lot faster ?...or do I ?

Does it have anything to do with the atmosphere moving also ?

Men are the same as women.... just inside out !!
Title: Re: You spin me right round baby right round !!
Post by: Soul Surfer on 27/01/2006 23:17:06
The earth is a lot bigger than a roundabout so the curve is less steep.  the earth turns in 24 hours and is about 25 thousand miles around its circumference so the speed at the equator is about 1000 miles an hour.  the centrifugal forece means that the acceleration due to gravity is slightly less at the equator than the poles.

For a circular orbit just above the equator the centrifugal force just balances out the acceleration due to gravity.  to do this you need a velocity of about 18,000 mph

The formula for centrifugal force is the square of the velocity divided by the radius of the curve.

The formula for calulating the acceleration due to gravity (in cm/sec^2)at any point on the earth's surface (from Child's physical constants) is:-

g = 980.616 - 2.5928 cos 2xlatitude + 0.0068 cos^2xlatitude - 0.0003 x height in meteres (above sea level)

The first correction of about 2.6/980 or 0.25% is the main bit due to the centrifugal force.

You can confirm the self consitancy of these three facts by noting that the increase in vlelocity between the earth's rotation and the orbit is about 20 and 20x20 is 400 or and 1/400 is 0.25%.

Learn, create, test and tell
evolution rules in all things
God says so!
Title: Re: You spin me right round baby right round !!
Post by: neilep on 29/01/2006 15:27:11
Thank You very much Ian.

Men are the same as women.... just inside out !!