Question

When a boy weighing 20 kg sits at one end of a 4 m long see-saw, it gets depressed at this end. How can it be brought to the horizontal position by an another boy weighing 40 kg?

• A. By sitting at a distance of 1m from two centres on the side opposite to the boy.
• B. By sitting at a distance of 4m from two centres on the side parallel to the boy.
• C. By sitting at a distance of 4m from two centres on the side opposite to the boy.
• D. By sitting at a distance of 1m from two centres on the side parallel to the boy.

Answer 1

The correct option is A

By sitting at a distance of 1m from two centres on the side opposite to the boy.

Weight of boy ( $W_1$) = 20 kg, $W_2$ ​ = 40 kg

Length of see-saw = 4m

Distance from centre = 2m

$W_1$​ $\times$ $d_1$​ = $W_2$​ $\times$ $d_2$​

20 $\times$ 2 = 40 $\times$ $d_2$​​

$d_2$​​​ = $\frac{20\times 2}{40}$ = 1m

By sitting at a distance of 1m from two centres on the side opposite to the boy, the long see - saw can be brought to the horizontal position.