Why is a seesaw balanced

Secure the block in place. Balance the ruler by placing equal masses for example, two coins on either side of the pivot. Note the distances the coins are from the pivot. Repeat using two coins on one side of the pivot and one coin on the other. Do your students notice any relationship between mass and distance? Encourage them to try with more coins. They may notice that if they double the mass on one side of the seesaw, it needs to be half the distance from the pivot.

Go into the playground and ask two children to volunteer to sit on the seesaw, one on each end. Ask pupils to work out how to make the seesaw balance. Once it is balanced, ask another student to measure the distance between each child and the centre of the seesaw the pivot and note it.

Ask a third child to take part in the experiment by sitting with one of the children already on the seesaw. Can the students work out how to balance the seesaw?

Test their theory and take down the measurements again. Seesaws are governed by a simple equation stating that to achieve balance, the force exerted on one end of the seesaw times the distance between the force and the pivot should equal the force exerted on the other side of the seesaw times the distance of that force from the pivot. The force is the mass of the object multiplied by g, the gravitational constant.

Therefore, if the mass on one side of the seesaw is larger than the mass on the other, its distance from the pivot needs to be shorter in order to balance the seesaw. This exploration requires at least two children! Does it balance? Which end is heavier? Why do you think so? What happens when one child or the other moves toward the middle of the seesaw? This may require some maneuvering on newer seesaws with large handles. Why do you think that happens? Taught By. Louis A. Bloomfield Professor of Physics.

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