Question

The plank of a seesaw is $8\text{m}$ long and is supported at the centre. Neil, who weighs $80\text{kgf}$ sits at a distance of $3\text{m}$ from the fulcrum. John sits $4\text{m}$ from the fulcrum to balance the plank. What is John's weight?

• A. 60

Answer 1

The correct option is A 60

Let John's weight be $\text{x kgf}$.
Given, Load = $80\text{kgf}$ (Neil's weight)
Load arm = $3\text{m}$
Effort arm = $4\text{m}$

We know that

$\text{Load}\times \text{Load arm}=\text{Effort}\times \text{Effort arm}$

$80\times 3=\text{x}\times 4$

$\text{x}=\frac{80\times 3}{4}$

$⟹\text{x}=60kg$

Hence, John's weighs $60\text{kg}$.