1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

I Spinning and the Earth

  1. Feb 24, 2017 #1
    Ok now I have a strange question. The earth is spinning continuously at a considerable speed. So if the Earth stopped spinning everything would be thrown by its momentum. But what would happen if for a split second you were no longer caught up in the Earths momentum. For example you are standing in the middle of a field and for one second the earth keeps spinning, but you don't spin along with it.
     
  2. jcsd
  3. Feb 25, 2017 #2

    Baluncore

    User Avatar
    Science Advisor

    Anything west of you that keeps moving will hit you at up to about 40 Mm/day = 463 m/sec.
    If you are going to try it, make sure you are 463 metres from the western barbed wire fence, prickly hedge or cattle.
    If you are facing west at the start of the second, you will fall on your face as your ankles break due to the supersonic surface speed. But to lie down would be good, because the wind from the west will also be supersonic, which will singe your eyebrows, strip your cloths and fill your lungs to bursting = air embolism = stroke.
    All things are relative, all relatives are things, your relatives would get your things.
     
  4. Feb 25, 2017 #3

    Nugatory

    User Avatar

    Staff: Mentor

    The consequences are less dire if you're farther away from the equator; a few tens of kilometers from the poles and you'd just experience a gentle breeze and the odd experience being chased by slow-moving terrain.

    However, the point about relatives is well-taken... Perhaps I should change my will?
     
  5. Feb 25, 2017 #4

    A.T.

    User Avatar
    Science Advisor
    Gold Member

    There are planes which can do it, even at the equator. Nothing special happens, unless you hit something.
     
  6. Feb 25, 2017 #5

    Baluncore

    User Avatar
    Science Advisor

    It would need to have pretty good acceleration and brakes to do it for just one second.
     
  7. Feb 25, 2017 #6

    Dale

    Staff: Mentor

    Hahaha!!!
     
  8. Feb 25, 2017 #7
    Depending on the local geography, you will with either end up in mid air, or else will end up as messy stain on a nearby hill.
    If the local geography near your field is absolutely flat like say the Netherlands, then you might get away with just your legs missing.
     
  9. Feb 28, 2017 #8
    If you were onboard a good ship at sea, you'd be pretty safe though.
     
  10. Feb 28, 2017 #9

    Baluncore

    User Avatar
    Science Advisor

    Assuming in the first place that the good ship also stopped moving at the same instant as you.

    Being at sea would worry me in those conditions. The hull speed of a boat is related to it's length and the wave making characteristics. In the region of the hull speed, the bow lifts and the stern settles into a hole below sea level. The view from the stern of a destroyer at top speed can be intimidating as you are below sea level with the stern wave breaking above you. More power will not push you much faster, it will just make the bow wave higher and the hole deeper until you sink stern first.

    The percussion wave from a sea mine destroys hulls efficiently. I expect the dynamic pressure of water against the hull at Earth rotation speed would destroy the hull integrity and remove the propellers pretty much instantly.

    If you were heading west as you stopped, the dynamic pressure of the moving water on the bow would become;
    Pa = ½ · 1000 kg/m3 · v2.
    At latitude 45°, the water speed will be about 0.7071 * 40k km/day = 1600 km/hour = 445 m/sec.
    That gives a dynamic pressure of; Pa = 100 MPa = 14,500 psi or 1000 atmospheres.

    Better you than me.
    They would ring the Lutine Bell at Lloyd's in London only once.
    https://en.wikipedia.org/wiki/HMS_Lutine_(1779)#The_Lutine_Bell
     
  11. Feb 28, 2017 #10
    Oh sorry everyone, I misread the OP in haste. I thought the question was what happens when the earth stops rotating for 1s (which is what is typically asked) - in this case, being onboard the ship would be the same as riding a tsunami. In the case of the OP scenario: You're completely right, the passenger would be dead.

    Why? Well, simple. m*dv = f*dt => if you're on board, for example, the Queen Mary, and heading north/south at the equator, your ship will receive an impulse of roughly 300*20*100*10^6Ns = 6*10^11 Ns, which will correspond to roughly a velocity of 6*10^11Ns/(150*10^3*10^3kg) = 400 m/s => you'll be turned into mush as you hit one of the walls. Obviously, if you're heading east/west wouldn't help matters much either.

    PS: And by the way, you're totally right that hull integrity would be completely lost. A modern submarine can only take about 7MPa of pressure before being crushed (crush depth =700m => P = 700m*1000kg/m^3*10N/kg), and these things are custom-built to withstand pressure.
     
    Last edited: Feb 28, 2017
  12. Feb 28, 2017 #11

    Baluncore

    User Avatar
    Science Advisor

    If a supertanker was found on the floor of the Atlantic, at latitude 45°, with the front 445 m crushed flat, would we entertain for even one second, the idea that the ship had suffered a 1 second loss of momentum, while on a course due west ?
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted



Similar Discussions: Spinning and the Earth
Loading...