(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

On its way to Paris the Eurostar train is travelling due South at 300 km/h

at a point with latitude 49°. Assume the Earth is a perfect sphere of radius,

R_{E}, that rotates around its axis (North/South pole) once every 23 hrs 56

min.

(a) Calculate the magnitude of the acceleration of the train due to the

Coriolis force. Note that latitude is defined as the angle [itex]\phi[/itex] with respect

to the North-South pole axis where [itex]\phi[/itex] = 0 at the equator and [itex]\phi[/itex] = 90° at the North pole.

(b) What direction is this acceleration in?

2. Relevant equations

Acceleration due to coriolis effect:

[itex]\vec{a}[/itex]_{co}= 2[itex]\vec{v}[/itex]×[itex]\vec{ω}[/itex]

where a_{co}is the accerlation due to coriolis effect, [itex]\vec{v}[/itex] is the velocity of the object in question and [itex]\vec{ω}[/itex] the angular frequency at that latitude.

3. The attempt at a solution

I know this question has something to do with 2 seperate reference frames, one inertial and one not, however for some reason I seemed to have ignored that completely and just attempted it this way:

First of all I calculated the angular frequency at 49 degrees latitude this way:

angular frequency at equator: [itex]\omega = 2\pi/\tau[/itex]

angular frequency at 49° latitude = [itex]\omega = (2\pi/\tau) cos(49°)[/itex]

[itex]\tau = 23+14/15[/itex] hours

Then I moved on to converting the velocity of the train into spherical co-ordinates. I did this via ratios rather than standard conversions because well, I don't really know it just seemed easier, it's probably where I've gone wrong, I've drawn a diagram on my sheet of paper but hopefully it'll make sense without it.

Ok so the train is travelling due south on the surface of the earth, with a velocity of 300 km/h, over a total distance of half the circumference of the earth (as the train is starting from a lower latitude it isn't actually covering this distance but hopefully that is irrelevant), what i'm looking for is [itex]\partial\phi/\partial t[/itex] and I calculated that:

[itex]\partial v/ \partial t / 0.5 Ce= (\partial \phi / \partial t) / \pi[/itex]

Where Ce = circumference of earth.

I then solved for [itex]\partial\phi/\partial t[/itex] and got this equal to 0.047 rad / hour in the [itex][itex]\widehat{\phi}[/itex] direction.

I then did the cross product of my angular frequency of the Earth at this point and the angular velocity multiplied by 2 and my result came out in the [itex]\widehat{r}[/itex] direction, and was negative so it is going into the planet. I know the drift should be to the left so I'm real confused.

I'm pretty sure I've approached it all wrong so I'd appreciate any help. Thanks.

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# Homework Help: The coriolis effect

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