Question

Two small kids weighing 10 kg and 15 kg are trying to balance a see saw of total length 5 m, with fulcrum at the centre. If one of the kids is sitting at the end, the other should sit at ____________

• A. 1.5 m from centre
• B. 1.6 m from centre
• C. 1.7 m from centre
• D. 1.8 m from centre

Answer 1

The correct option is C

1.7 m from centre

To balance the see saw, let the second kid is sitting at a distance of 'x' m from the fulcrum.
In rotational equilibrium, $T_{net}=0$ about fulcrum.
$\Rightarrow {\tau }_1={\tau }_2$
$\Rightarrow \left(10kg\right)g\left(2.5\right)=\left(15kg\right)\left(g\right)x$
$\Rightarrow \frac{10\times 2.5}{15}=x\Rightarrow x=1.7m$ from centre