Torque balance on a seesaw
A 40 kg child sits 1.5 m from a seesaw's pivot. How far from the pivot must a 60 kg adult sit on the other side to balance it?
Answer B: explanation for every choice
A
At 0.75 m, the adult's side gives 60 × 0.75 = 45 kg·m (times g), less than the child's 40 × 1.5 = 60 kg·m.
B
Correct. Balance requires m₁d₁ = m₂d₂: 40 × 1.5 = 60 × d, so d = 1.0 m.
C
Equal distances ignore the difference in mass. The heavier adult would tip the seesaw.
D
This inverts the mass ratio. At 2.25 m the adult's torque would be more than double the child's.
TakeawayBalance when clockwise torque equals counterclockwise torque: m₁d₁ = m₂d₂.
Equation usedTorque
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