Re: pinhole coriolis effect demo.

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From: Paul Doherty (pauld@exploratorium.edu)
Date: Thu May 06 2004 - 17:11:55 PDT 

Message-Id: <l03110725bcc083878823@[192.168.112.30]>
Date: Thu, 6 May 2004 17:11:55 -0700
From: Paul Doherty <pauld@exploratorium.edu>
Subject: Re: pinhole coriolis effect demo.

Hi Kevin

You are correct.

Consider a cannon ball fired horizontally to the north from the equator.
The equator is moving 1000 miles per hour to the east. So the canon ball
goes north and east at the same time. So for short distances the observer
sees the ball go straight north because everythin:, ground, air and ball,
moves east at the same rate.

However if it goes far enough north it comes to a place where the surface
of the earth is going east along with the air at a slower rate, at 45
degrees north the surface moves at 700 mph to the east. But the cannon ball
is still going east at 1000 mph so it pulls ahead of the surface and the
air and seems to curve. (Even though viewed from space its moving in a
straight line.)

Paul D

>Recently my class and I were reading about the Coriolis Effect. There was a
>hypothetical analogy of firing a cannon ball from the North Pole toward the
>Equator. The description went on to say that the cannon ball would appear to
>not travel in a straight line due to the revolution of the Earth underneath
>the flying projectile. This seems to make sense but, would the cannon ball
>turn with the Earth due to inertia/momentum just as a ball thrown in the air
>by a passenger on a moving vehicle would continue its forward motion even if
>the vehicle stopped before the ball landed?
>
>Would there be any 'forward motion' if fired from the actual N. pole?
>
>I know this is potentially more complicated but is the cannon ball analogy
>sound enough for helping to explain the Coriolis Effect?
>
>P.S. I'm assuming that the flying cannon ball is analogous to 'flying' air
>molecules that are not directly attached to terra firma.
>
>Thanks for you input,
>
>Kevin Kinsella
>5th/6th Science Explorer
>Woodside School
>
>650.851.1571 x256
>
>
>
>
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