Page 1 of Is this true?

I can`t see how it can be, but...

25. A duck`s quack doesn`t echo and no one knows why.

Anyone?

how about this one to bake your noodle:

two points on a fixed disc (e.g. a record or a cd), one on the outer rim and one near the centre.

both points take the same amount of time to do one full revolution and travel at the same speed, yet the point on the outer rim covers more distance than the point near the centre - how is this?

(i know it has nothing to do with ducks and quacks but, hey, i`m bored... )

A duck`s quack doesn`t echo and no one knows why
This has been mentioned before
http://www.dvd.reviewer.co.uk/forums/thread.asp?Forum=113&Thread=163500&Page=10&Type=1 page 10

http://www.snopes.com/critters/wild/duckecho.htm

But they don`t travel at the same speed do they. Not sure what the confusion is here? Have I missed something?

Jack Turnip the time travelling duck from the 87th century says my quack echoes

I suspect this lie has propagated for the simple reason that most people hear ducks on lakes or ponds, where there is surrounding foliage, and no solid objects to reflect the sound of them quaking.

So if you have never heard a duck`s quak echoing, which lets face it most of us haven`t, then there is a good chance you`ll believe that they don`t echo if someone tells you its true.

Why are there never any baby pigeons? is another good one. Outside of a nest, most people don`t see any baby birds, but pigeons get singled out for some unknown reason. :)

Editor
DVD REVIEWER

"both points take the same amount of time to do one full revolution and travel at the same speed"

No, that can`t be correct.

Speed = distance / time
Take a disc rotating at (say) 1 revolution per second. Radius to outer rim = 10cm, Radius to inner point = 2cm.
Distance travelled in 1 second (i.e. 1 rev) by outer point = 2 x 10cm x 3.14 (pi) = 62.8cm

So speed of outer point = 62.8cm/second.

Distance travelled in 1 second by inner point = 2 x 5cm x 3.14 (pi) = 31.4cm

So speed of outer point = 31.4 cm/second.


QED

They definitely don`t travel at the same speed.

Can`t remember the official term for it, angular velocity I think would be the same for both as they both travel through the same number of degrees.

Their actual linear velocity (speed in layman`s terms) is different, it gets faster as it moves away from the centre of the disc.

"Radius to inner point = 2cm."
"Distance travelled in 1 second by inner point = 2 x 5cm x 3.14 (pi) = 31.4cm"
Surely if inner rad = 2 then distance = 2 x 2 x Pi = 12.6cm/s

"So speed of outer point = 31.4 cm/second."
No, it`s 62.8cm/s like you said.

Angular velocity is really measured in radians/sec though.

Anyway, yeah it goes faster the further away from the centre..

Ste