Naked Science Forum

Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: thedoc on 14/06/2012 17:30:01

Title: If the earth stopped spinning, how much heavier would things become?
Post by: thedoc on 14/06/2012 17:30:01

Rex van der Spuy  asked the Naked Scientists:
   
Hello!

I know that the rotation of the Earth creates centrifugal force that counteracts the force of gravity.

If the earth stopped spinning, how much heavier would things become?
Would we all be crushed by the force of gravity?

Thanks so much!!!

Regards,

Rex

What do you think?

Title: Re: If the earth stopped spinning, how much heavier would things become?
Post by: syhprum on 14/06/2012 22:20:27

The reduction in weight at the equator due to Centrifrugal force (sorry Geezer) amounts to 0.35% and is of course zero at the poles.

Title: Re: If the earth stopped spinning, how much heavier would things become?
Post by: CliffordK on 15/06/2012 00:27:18

Of course, without the spin, the Earth would not have an equatorial bulge.  If the spin suddenly stopped, perhaps the bulge would rearrange itself quickly.  Anyway, without the bulge, the gravity would be higher than calculated at the equator, and less than calculated at the poles.

Title: Re: If the earth stopped spinning, how much heavier would things become?
Post by: Geezer on 15/06/2012 07:44:47

Quote from: syhprum on 14/06/2012 22:20:27

The reduction in weight at the equator due to Centrifrugal force (sorry Geezer) amounts to 0.35% and is of course zero at the poles.

Far be it for me to burst anyone's bubble. Should they wish to believe in the Tooth Fairy, the Easter Bunny, and the Solstice Amphibian, that's entirely up to them, but this is a science forum, so those who choose to refer to forces centrifugal might at least point out that these are pseudo-forces.
 
They seem very real, but they are actually imagined (just like the Tooth Fairy, the Easter Bunny, and the Solstice Amphibian).

Title: Re: If the earth stopped spinning, how much heavier would things become?
Post by: syhprum on 15/06/2012 20:32:45

I only used the dreaded C word because that is how the originol correspondent refered to the centripetal acceleration as you may surmise he was rather confused as to magnitude of this effect.

Title: Re: If the earth stopped spinning, how much heavier would things become?
Post by: Geezer on 17/06/2012 01:31:41

Good point!

For the benefit of the correspondent, we can state that gravity produces a centripetal force (acting towards the center of the Earth) and that centripetal force can be reduced slightly because our mass would prefer to follow a tangential path relative to the Earth's surface - IOW, it would prefer to go straight on, but in this case, gravity wins, so we stay "attached" to the Earth.

This naturally prompts another related question:

How short would the terrestrial day be if objects at the equator did not stay attached to the Earth?

Title: Re: If the earth stopped spinning, how much heavier would things become?
Post by: RD on 20/06/2012 01:04:27

Quote from: Geezer on 17/06/2012 01:31:41

How short would the terrestrial day be if objects at the equator did not stay attached to the Earth?

Assuming Earth was solid and didn't deform, (which it would as it's mostly liquid / ductile), 84 minutes ...

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http://exploration.grc.nasa.gov/education/rocket/rktrflght.html


Wikipedia makes it 85 minutes ... http://en.wikipedia.org/wiki/Orbital_speed#Earth_orbits