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Old 2009-03-31, 11:06   #1
Andi47's Avatar
Oct 2004

248210 Posts
Default How fast is the dog?

A dog decides to run 500 km. It has got an empty cane tied on its tail, which hits the ground exactly once every second with a loud "clonk!" sound.

The dog starts its run with the first clonk it hears, with a velocity of 2 m/s. Afterwards it doubles its velocity instantly (i.e. with infinite acceleration) every time when it hears a clonk from the cane.

How fast is the dog when it reaches its destination?
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