Question

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.

Answer 1

A seesaw is an example of a lever with its fulcrum (pivot) placed at the center. To keep the seesaw balanced, the clockwise and anticlockwise moments must be equal.

effort × effort arm = load × load arm

i.e., (weight of child) × (distance of child) = (weight of adult) × (distance of adult)

Suppose the child's weight is W and the adult's weight is 2W. If the child sits at a distance d_child​ and the adult sits at a distance d_adult​ from the fulcrum, then:

W × d_child ​= 2W × d_adult​

Dividing both sides by W:

d_child ​= 2 × d_adult​

Therefore, the child should sit twice as far from the fulcrum as the adult to balance the seesaw. For example, if the adult sits 1 m from the fulcrum, the child should sit 2 m from the fulcrum.