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A long uniform wooden board (a playground see-saw) has a pivot point at its center. An older child of mass M=32 kg is sitting a distance L from the pivot. On the other side of the pivot point are two smaller children each of mass M/2. One is sitting a distance L/6 from the pivot. How far from the pivot must the other small child be sitting in order for the system to be balanced?

Respuesta :

Answer:[tex]\frac{5L}{6}[/tex]

Explanation:

Given

Wooden board is pivoted at center and

Older child of mass [tex]M=32\ kg[/tex] is sitting at a distance of L from  center

if two child of mass [tex]\frac{M}{2}[/tex] is sitting at a distance [tex]\frac{L}{6}[/tex] and [tex]x[/tex](say) from pivot then net torque about pivot is zero

i.e.

[tex]\Rightarrow \tau_{net}=MgL-\frac{M}{2}g\frac{L}{6}-\frac{M}{2}gx[/tex]

as [tex]\tau_{net}=0[/tex]

Therefore

[tex]MgL=\frac{M}{2}g\frac{L}{6}+\frac{M}{2}gx[/tex]

[tex]L-\frac{L}{6}=x[/tex]

[tex]x=\frac{5L}{6}[/tex]

Therefore another child is sitting at a distance of [tex]\frac{5L}{6}[/tex]

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