Naked Science Forum

Non Life Sciences => Technology => Topic started by: purplerain on 04/04/2011 17:30:02

Title: How does scratching a coin make it work in a machine?
Post by: purplerain on 04/04/2011 17:30:02
Tahnee asked the Naked Scientists:
   
Why do the pay on foot machines have a scratch-area so that the coins that wont work, work after scratching them?

What do you think?

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