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Bird Velocity and Acceleration
Name: Gavin F.
Status: educator
Age: 20s
Location: N/A
Country: N/A
Date:
Monday, September 30, 2002
Question:
I would like to know of a way of measuring the speed and
acceleration of flying birds. This would appear to be a straightforward
problem but on reflection it is not so easy! In practice radar or laser
guns would be difficult to operate and would require the observer to
know to angle from bird to device at all times. Using video to measure
the time taken for a bird to pass between points a known distance apart
would give a measure of speed but not acceleration. So what is the
answer, wind tunnels? Is there a simple answer I am missing. Help!
Replies:
Gavin,
The acceleration of a bird will not be constant, so you have to determine
what interval of the flight you wish to measure it for (what you will get
is average acceleration over that interval). However, measuring the time
of flight for a known distance via video can get you acceleration as well,
by breaking up its travel into smaller pieces.
Speed = change in distance/time
Acceleration = change in speed/time = (final - initial speed)/time
First we have to assume that you can get a decent measure of speed- you
have known points and the bird flies more or less in a straight line
between them.
The timing between frames of a video should be constant, so if you have
good indicators of distance, you can determine speed for any part of the
flight by the distance travelled between frames.
Measuring acceleration from rest is the easiest, since you know initial
speed is zero. Measuring from other points will be more difficult,
depending on your ability to measure distance and speed accurately from the
video.
Don Yee
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Update: June 2012
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