A see-saw is balanced about its pivot. A 30 kg child sits 2 m from the pivot on one side and a second child sits 0.5 m from the pivot on the other side. Ignoring the see-saw's own weight, what is the mass of the second child?
Answer and explanation
Correct answer: D. 120 kg
- Step 1: For balance, clockwise moment = anticlockwise moment: .
- Step 2: kg.
Answer
120 kg.
Why not the others: 7.5 kg: it swaps the two distances. 31.5 kg: it adds and subtracts the numbers. 30 kg: it multiplies all three values.
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