Question

3. A 40 kg boy sits 1.2 m from the fulcrum of a see-saw. Where should another boy of 30 kg sit on
the other side in order to balance it?​

Answer 1

Answer:

1.6m

Explanation:

Torque 0f 40kg weight must be equal and opposite totorque of 30kg weight

Torque =force×arm length

40kg×g×1.2m=30kg×g×x

X=1.6m

Answer 2

Answer:

Another boy sits 1.6 m from the fulcrum.

Explanation:

Given that,

Mass of boy = 40 kg

Distance = 1.2 m

Mass of boy = 30 kg

Let the distance from the fulcrum where the another boy sit be x.

We need to calculate the another side

The moment of force on both side of the fulcrum must be same to the balance.

$F\times d=F'\times d'$

$mg\times d=m'g\times d'$

Put the value into the formula

$40\times9.8\times1.2=30\times9.8\times x$

$x=\dfrac{40\times9.8\times1.2}{30\times9.8}$

$x=1.6\ m$

Hence, Another boy sits 1.6 m from the fulcrum.