A boy and a girl are balanced on a massless seesaw. The boy has a mass of 75 kg and the girl's mass is 50 kg. If the boy sits 2.0 m from the pivot point on one side of the seesaw, where must the girl sit on the other side?

The girl must sit 5 m on the other side of the seesaw.

Explanation:

Given;

mass of the boy, = 75 kg

mass of the girl, = 50 kg

distance of the boy from the pivot, = 2 m

let the distance of the girl from the pivot = d

    <2m><d>

     ↓                                  Δ                                   ↓

     75                                                                      50

Apply the principle of moment, about the pivot;

clockwise moment = anticlockwise moment

75 x 2 = 50 x d

150 = 50d

d = 150 / 50

d = 3 m

The distance of the girl from the pivot is 3 m.

Therefore, the girl must sit ( 2m + 3m ) on the other side of the seesaw.