# Tag Info

12

The whirl is due to the net angular momentum the water has before it starts draining, which is pretty much random. If the circulation were due to Coriolis forces, the water would always drain in the same direction, but I did the experiment with my sink just now and observed the water to spin different directions on different trials. The Coriolis force is ...

7

The answer: the ball appears to be deflected ~10 cm. The calculation: For simplicity, say we tee off at the north pole. The effects are a bit weaker at more typical locations, you multiply by sin(latitude) = 0.64 for a 40 degree (central california or washington DC) latitude. The Coriolis effect exists because the Earth rotates while the ball is in ...

5

Since you want to explain it to your daughter, take a plastic bottle, cut the bottom open, turn it upside town, hold the top closed and fill it with water. Give her that bottle and have her release the top (which is on the bottom now, sorry for the bad phrasing). The water will whirl in different orientations whenever you repeat this (if it whirls at all) ...

4

An alternate derivation for a due-north ball, ignoring the diminishing effect of latitude, that confirms Kevin's order of magnitude: Acceleration due to the Coriolis effect: $a_C = -2 \, {\Omega \times v}$ $\Omega = 2 \pi/day$ $v = 45 m/s$ $a_C = -0.00654498469 m/s^2$ Horizontal displacement $d$ is given by $d = 1/2a_C\,t^2$ Using earlier estimate of ...

3

Well, there is a partial yes that is a direct result of the Coriolis force: If you go up in a hot air balloon, you will be subject to various winds which will move you. And these winds are a result of the Earth spinning. In principle you should be able to navigate to most places on the globe by choosing height etc. in reality it is much too complex to do ...

3

The whirl happens in the draining tube, whose optimal solution to drain the bathtub is a laminar flow allowing for some rotation in the tube. What you see in the surface is the match between the solution of flow in the tube and the solution of flow in the surface. Angular momentum of the flow gets modified a lot as the tube twists and twists, sometimes even ...

2

You can think about it like this: It takes one day for the earth to perform a full rotation (about 86k seconds), on the other hand, it takes a few seconds for your sink to drain (lets say 10 seconds). So it takes 8600 times longer for the earth to do a full rotation than it takes the water to drain down the sink. It is not too hard to imagine that the ...

2

Firstly, is that correct? Yes you're intuitive understanding for this part of the Coriolis effect is correct. The second part, that is, why wind in the East direction is deflected South, is a bit trickier, and involves the use of centripetal force. this is given by the equation: $F = \frac{mv^2}{r}$ If we re-arrange the above equation, we can find ...

2

I am not particularly an expert either, but my understanding is that shuttle flight is a very active process compared to ballistic motion, so any effects the Coriolis effect might have can just as well be considered as additional errors in the trajectory, which is being adjusted. There's an active feedback loop at work: "observe flightpath -> identify ...

2

The Coriolis acceleration goes like $-2\omega \times v$, which for the sake of an order of magnitude estimate we can take to be $a\sim \omega v$. But in order to get an observable effect, we don't just need an acceleration, we need a difference in acceleration between the two ends of the tub, which are separated by some distance $L\sim 1$ m. The ...

2

The calculation of the Coriolis force is dependent on latitude: $F = m a$ where $a = 2 \Omega sin(lat)$, with $\Omega$ being the Earth's angular velocity $m$ is the mass of the object in question The Earth's angular velocity is (about) $7.29 \times 10^{-5}$ rad/sec So, for a sink with a couple gallons of water in it at 45 degrees north... the Coriolis ...

2

Well, first we know that the Coriolis force acting on the scale of a toilet is going to be a pretty small force. So the question can generally be tackled in the following way: Estimate the magnitude of the Coriolis force on the toilet water. Use this to estimate the magnitude of effect of the Coriolis force on the toilet water spin. Enumerate the ...

2

The Coriolis effect cannot possibly account for this. Other factors (e.g the shape of the basin and initial conditions for the water flow) should have a comparatively huger effect. This is intuitively obvious---if you are not convinced you should perform an experiment. Could be fun! You could also estimate characteristic scales (via dimensional analysis) ...

2

Rockets lean as they climb on purpose, in order to obtain the high orbital velocities needed to stay in space once they get there. For a nice explanation, see Orbital Speed at xkcd what-if, but the gist is the following. Being in orbit means going so fast that the Earth begins to curve away from you as you fall down towards it. The classic image to keep in ...

2

The rotation of your coordinate system causes the Coriolis effect. Things move in straight lines, but if your coordinate system is rotating, then the straight lines look curved from the perspective of your coordinate system. If you want to insist that objects move in straight lines in your coordinate system, then you must invent a fictitious reason why ...

1

Here's how you might proceed analytically. On the surface of the Earth, the Earth's rotation causes the introduction of fictitious forces. The total effective apparent force is $$\mathbf F_{\mathrm{eff}} = \mathbf F_{\mathrm{ext}} + m\mathbf g_{\mathrm{ eff}} - 2m\vec\omega\times\mathbf v$$ The last term is the Coriolis term where $\vec\omega$ is the ...

1

There is no significant difference between what happens in the east-west direction and what happens in the north-south one. Upon impact it will experience a pretty sudden acceleration due to the impact, and depending on the trajectory and the nature of where it hits the ground, it may not stick, but rebound, skid, or whatever...

1

OK, this isn't really an answer since I honestly don't know what the answer is but I Googled "shuttle autopilot coriolis effect" and the 2nd link was this: Design of the space shuttle digital autopilot and resulting dynamic environment "CORIOLIS EFFECT" is one of the key words for the document. It's old and not available digitally but you can request it. ...

1

[Moved this answer from here.] Consider this picture of water running from a faucet: The stream narrows as it falls. The shape of the stream has a definite mathematical shape, which follows from (1) conservation of energy, (2) conservation of mass, and (3) the approximation that the horizontal velocity of the water makes a negligible contribution to its ...

1

A discussion by 'The Straight Dope' website http://www.straightdope.com/columns/read/149/do-bathtubs-drain-counterclockwise-in-the-northern-hemisphere references experimental work carried out but Ascher Schapiro in 1962, which concluded something like it all depends on the shape of container and how its stirred before being left to empty. Here is ...

1

The main effect is angular momentum (rotational inertia) in the water set up by various movements before you start observing, such as getting out of your bath. This results in the water level being lower near the centre of rotation than further away, setting up centripital forces which maintain the rotation. When the difference in levels is significant ...

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