Do You Know What Is a Seesaw Used for?

Seesaw game is a common game which kids love to play. Sometimes adults also like to indulge in the joyful of seesaw. It looks so simple, and only need a board with a fulcrum. The board material can be metal, wood or plastic. Of course, the metal seesaw is heavy and firm, since it has good load weight capacity. So it is the most common outdoor seesaw. And wooden seesaw is easy to broken and moldy if it is exposed outside for a long time. Plastic seesaw is suitable for children, it is light and easy to move, so it is often installed at home as indoor seesaw. The seesaw game is a kind of group game, which needs at least two or more people to play together. One people cannot play it. And usually it requires the weight of people balanced on each end when operating correctly. Then what principle does the seesaw use? In this article, we will tell you some knowledge about the seesaw.

People who learned physics in middle school know that the seesaw uses the principle of leverage. The long board of kids’ seesaw can be looked as the equal arm lever. The fulcrum in the middle decides the balance of board in the condition of same weight on each end. We know that Lever is also called labor-saving lever, equal arm lever. The principle of leverage is also called the lever balance condition. To balance the lever, the two moments acting (the product of the force and the arm) on the lever must be equal in magnitude. That is to say power × dynamic arm = resistance × resistance arm. If it is expressed in algebraic formula as F1·L1=F2·L2. In the formula, F1 represents power, L1 represents power arm, F2 represents resistance, and L2 represents resistance arm. It can be seen from the above formula that to balance the lever, the power arm is several times the resistance arm, and the resistance is several times the power. 

Generally speaking, there are two situations of lever force: 

1. There are only two forces on the lever: power × distance from fulcrum to line of action of power = resistance × distance from fulcrum to line of action of resistance. That is to say, power × power arm = resistance × resistance arm, that is F1×L1=F2×L2.

2. There are multiple forces on the lever: the product of the force that makes the lever turn clockwise and its stress arm is equal to the product of the force that makes the lever turn counterclockwise and its stress arm. This is also known as the principle of reciprocity of leverage, and it also applies to situations where there are only two forces.

According to above principles, an adult can play the outdoor seesaw with a child, the way is to move the distance between an adult and fulcrum. Is it simple? In fact, people know it when playing, if it is explained in physics, it looks complicated. Nowadays, the principle of small seesaw has been widely used in our daily life and brings more convenience for us.