Question

Two children weighting 20kg and 25kg wanted to balance a seesaw of length 4m pivoted at its mid point.A child of 20kg is sitting at one edge of the seesaw.Where should the other child sit so that the seesaw is exactly balanced

Answer 1

Given:

Two children weighting 20kg and 25kg wanted to balance a seesaw of length 4m pivoted at its mid point.A child of 20kg is sitting at one edge of the seesaw.

To find:

Position of sitting of 25 kg child?

Calculation:

For the see-saw to achieve ROTATIONAL EQUILIBRIUM, the torque due to 20 kg child and 25 kg child should be equal and opposite.

• 20 kg child is sitting 4/2 = 2 m from midpoint
• Let 25 kg child sit x metres from midpoint.

$\therefore \: \tau_{(20 \: kg)} =\tau_{(25 \: kg)}$

$\implies( 20g) \times 2 =( 25g)x$

$\implies x = \dfrac{20}{25} \times 2$

$\implies x = 1.6 \: metres$

So, 25 kg child has to sit 1.6 metres from midpoint.