Final answer:
To determine where an additional 20 kg child should sit to balance the seesaw, we apply the concept of torque and the conditions for equilibrium, which state that the torques on either side of the pivot must be equal.
Step-by-step explanation:
To find where another 20 kg child should sit in order to balance the seesaw, we use the concept of torque and the condition for equilibrium. Torque (τ) is the product of the force applied (in this case, the weight of the child) and the distance from the pivot point at which the force is applied (r). For a seesaw to be balanced, the torques on either side of the pivot must be equal, giving us the equation τ1 = τ2, or m1r1 = m2r2. From the available information, it is established that r2 for a child weighing 26.0 kg is 1.30 m, and this child will be sitting closer to the pivot than the lighter child who has to sit farther away to maintain balance. Therefore, if we place another child weighing 20 kg on the seesaw, they should sit at a distance similar to that of the 20 kg child already balanced on the seesaw, which is not given in the question, but the principle would remain the same: the distance would have to fulfill the equilibrium τ1 = τ2.