Working of railway-platform weighing machines

Let me tell you, weighing machines accept the right coins only.A railway station has an atmosphere of its own. The bustling activity, the trains - coming in or leaving the station, the vendors - trying hard to sell their goods. And yes, your favorite feature -the automatic weighing machine. I know, all of you love to use it. Whenever you enter the platform, this machine with colourful blinking lights attracts your attention. And it’s so easy to know your weight. Just step on the pedestal put a coin into the machine and you come to know your weight. But what if the coin is a counterfeit? Will the machine know the difference? Certainly yes. When a coin is put into the machine, an electric current passes through it. Only a genuine coin conducts the right amount of electricity and is accepted by the machine. Other coins are rejected.The coins then roll by a magnet that attracts it, slowing it down. Thus the machine uses electrical, magnetic and weighing tests to make sure that the coins are real. So, never try to insert other objects into the coin hole. You will only damage the machine, which is not the right thing to do. Nowadays we have automatic vending machines for selling milk, cold drinks and ice-creams also.

Web references :

Archemedies

Archimedes and the Golden Crown

Principals Of Buoyancy