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a penny
The question does not make sense because copper is a metal.
The density of a penny is higher.
acid and coke
Salt water will rust a penny faster than vinegar because salt water is an electrolyte that enhances the electrical conductivity, accelerating the oxidation process on the surface of the penny.
The penny will drop faster than the feather due to the difference in mass and air resistance. The feather experiences more air resistance, which slows down its fall compared to the penny.
the chemacls in vinager makes the penny rust
A common penny has a value of 1 penny only
....1 cent. It is common and found in change. While technically the metal value of it is around 2.8 cents, it is nearly impossible to get anyone to pay that much for a copper penny unless you are selling in bulk.
Copper or zinc
The orange juice must make the penny rust faster because when put a penny in a dish of lemon juice, it makes it shinier... which also works with ketchup.
An apple falls faster than a penny. The penny's flat surface creates more wind resistance than the round apple. And as Galileo observed, it depends on wind resistance, not weight.