Seesaws are common playground fixtures. They are fun to use and easy to construct. They are simple machines.
Structure of a Seesaw
A seesaw is a board balanced on top of a pivot point called a fulcrum. The fulcrum can be as simple as a log or specially designed to contain a bearing for smooth operation.
Technically, a seesaw is a first class lever, since the fulcrum is between the input and output loads (the riders). On a seesaw, the fulcrum is placed at the exact halfway position on the board.
Balancing a Seesaw
The board of a seesaw has equal lengths on either side of the fulcrum. The pivot point cannot be changed, so riders must adjust their positions (closer or further from the fulcrum) to achieve balance and make it easy for both riders to move up and down.
A fulcrum could conceivably be constructed from a wedge having a wide base on the ground, and a narrow edge under the seesaw board. It's not practical though, because there is no good way to prevent the board from changing its position on the wedge.
Although it would have no practical purpose, a seesaw with one end fastened to the ground makes an inclined plane.
- Motion, Forces, and Energy, 2002, Peter Kahan, Prentice Hall, Upper Saddle River, New Jersey
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