Do We Sense the Rotation on a Rapidly Spinning Planet?

[Frodo]

It's often said that you don't feel Earth rotation because the gravity acts against the centrifugal force.

Of course this is true but also your body is turned around once each 24 hours.

So I wonder on a planet which is rotating once each 3 seconds and has same g=9,81:

Would you feel the rotation?

I don't agree with your first sentence - it is wrong. Lots of things on Earth "feel" the Earth's rotation. It is just that the Earth's rotation is so slow so that you need something which takes a long time to see the effect.

1. See Foucault's Pendulum. It "feels" the Earth's rotation in as much as it remains oscillating in its initial direction which remains fixed with respect to the stars. The Earth rotates so the pendulum appears to rotate. Its direction of oscillation "rotates" once in 24 hours at the pole (actually - it does not rotate - it stays still and the easrth rotates below it!) and even more slowly at lower latitudes until it does not rotate at the equator.

2. When a battleship fires a shell north or south the aiming computer has to make an allowance for the Earth's rotation because, relative to Earth's surface, the shell travels in a curved path to the left or right depending on the hemisphere.

3. Look at a chart of ocean currents or winds. See how they all flow in circular paths - antii=-clockwise in the northern hemisphere and clockwise in the southern hemisphere. That is because of the Earth's rotation.

Do some research on Coriolis Force.

It is easy for you to model a planet rotating once every three seconds.

1. Find a playground with a child's roundabout.
2. Get on it and set it rotating at one turn every three seconds. You are now modelling standing close to the north pole of the planet.
3. Roll a ball radially towards the centre of rotation and observe that, relative to the roundabout/planet, the ball does not travel in a straight line. Bingo - you have observed that the roundabout/planet must be rotating.
4. Or stand up and try to kick towards the centre - you will think that an invisible gorilla grabs your leg and forces it sideways.

If you have one of those old fashoined things called a record player set it rotating and roll a small ball across the turntable. Notice how it does not follow a straight path relative to the turntable.

 

[DrStupid]

Lots of things on Earth "feel" the Earth's rotation.

I think he doesn't mean "feel" but feel (without quotation marks). The question (at least to my understanding) is: Could you directly sense something with your own body - not indirectly by observation of other objects? For a rotational period of 24 h this is obviously not the case.

 

[Frodo]

If the poster sat on the bob of a Foucault pendulum they would see the floor below them rotating as they swung.
They might not feel it as the effect is rather small but they would certainly see it.