A see-saw is balanced about its pivot. A 40 kg child sits 2 m from the pivot on one side and a second child sits 0.8 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: B. 100 kg
- Step 1: For balance, clockwise moment = anticlockwise moment: .
- Step 2: kg.
Answer
100 kg.
Why not the others: 16 kg: it swaps the two distances. 41.2 kg: it adds and subtracts the numbers. 64 kg: it multiplies all three values.
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