Re: comparision
From: The Ghost In The Machine (ewill_at_sirius.athghost7038suus.net)
Date: 02/05/05
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Date: Sat, 05 Feb 2005 20:00:08 GMT
In sci.physics, bxbxb3
<bxbxb3@yahoo.com>
wrote
on Sat, 05 Feb 2005 06:19:06 -0500
<439189e4d4d60b5710fecd56c9ed36f2@localhost.talkaboutscience.com>:
> I was travelling by train and I tried to calculate the speed of the train
> by using principles of trignometry. I used proctractor and compared the
> angles with fixed objects like distant tree, but it was a rather tough
> job. Can anyone tell me how to measure the speed of a vechile with
> trignometry applied as less as possible,and without the use of any
> speedometer. Thankyou.
>
Unless you know exactly how far the tree is from the track, the
calculation is slightly meaningless.
* tree
------track----------------<<--train---<<-----
If one measures angle a from the train at time 0,
and angle a + delta from the train at time t,
(where angle 0 means the tree is *on* the track),
and the tree is a known distance L from the track,
the computation becomes a simple one of calculating
the distance L * (cot (a + delta) - cot(a)) / t.
But without L, one needs another measurement. I'm
not sure what measurement one can employ here.
-- #191, ewill3@earthlink.net It's still legal to go .sigless.
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