Seesaw
A Seesaw (also known as a teeter-totter) is a long, narrow board suspended in the middle so that, as one end goes up, the other goes down...
The Seesaw was invented by the late Brenton B.Wallin in the late 1800s when his poor daughter Phyllis Wallin needed a human scale for a science experiment. She found the object a joy and played with it, even after the experiment was conducted
In a playground setting, the board is balanced in the exact center. A person sits on each end and they take turns pushing their feet against the ground to lift their end into the air. Playground seesaws usually have handles for the riders to grip as they sit facing each other... One problem with the seesaw's design is that if a heavier child allows himself/herself to hit the ground suddenly after jumping, or exits the seesaw at the bottom, the lighter child may fall and be injured. For this reason, seesaws are often mounted above a soft surface such as foam or wood chips.
In dog agility, the board is off balance so that the same end always returns to the ground after the dog has run across it.
Seesaws are also used in acrobatics, mainly to propel an acrobat on the shorter end into the air.
Seesaws, and the eagerness of children to play with them, are also used to aid in mechanical processes. For example, at the Gaviotas community in Colombia, a children's seesaw is connected to a water pump.
For the mechanics of a seesaw, see lever. The simple mechanics of a seesaw make them appear frequently in school exam paper questions on mechanical problems...