It depends what playground it is; they can be various sizes.
The Playground Kidders are the playground kidders
The unit meter is taken as the standard unit of length.As the play grounds are really big it would be foolishness to measure it with a smaller unit like centimeter or large units like kilometers or miles.The standard football ground in 90m in length.So it would be foolishness to say that it is 9000cms or 9/100 kilometers.The meter is the appropriate unit to measure that.
Either can be correct, depending on its use in a sentence: "Mel and I are at the playground" or "She found Mel and me at the playground."
Trash and old playground items to be replaced by new playground items.
The noun playground is a countable noun. Singular: playground Plural: playgrounds
playground equipment
No, it is not a preposition. The word playground is a noun.
A playground has no fixed size
Marshmellow Playground was created in 2010.
Snakes in the Playground was created in 1992.
Emotional Playground was created in 1991.