For rotational balance, effort times effort arm equals load times load arm. Since the adult has twice the weight of the child, the child must sit at twice the distance from the fulcrum compared to the adult.
On a seesaw with sliding seats, a child is sitting on one side and an adult on the other side. The adult weighs twice that of the child. The seesaw however is balanced. Draw a figure which depicts this situation showing the distances from the fulcrum where the child and the adult are seated.
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To achieve balance on a seesaw, the principle of moments applies, meaning load multiplied by load arm equals effort multiplied by effort arm. The adult exerts double the downward force of the child. Therefore, to balance the turning effects, the adult sits at a distance d from the central fulcrum, while the child sits on the opposite side at a distance 2d from the fulcrum.
For more NCERT Solutions of Class 9 Science Exploration Chapter 7 Work, Energy and Simple Machines Question Answer (2026-27)
https://www.tiwariacademy.com/ncert-solutions/class-9/science/exploration-chapter-7/