Answer:
The mother should sit at a distance of 4.5 ft from the fulcrum on the opposite side to the boy
Explanation:
Data provided in the question:
Distance of boy from the fulcrum, x₁ = 6 ft
Weight of the boy, W₁ = 90 lb
Weight of the mother, W₂ = 120 lb
let the distance of mother from the fulcrum be 'x₂'
Now,
Using the law of the lever equation:
W₁x₁ = W₂x₂
or
90 × 6 = 120 × x₂
or
540 = 120 × x₂
or
x₂ = 4.5 ft
hence,
The mother should sit at a distance of 4.5 ft from the fulcrum on the opposite side to the boy