Question

A 40 kg boy sits on a seesaw 2.0 m from the fulcrum. What distance from the fulcrum should a 30 kg girl sit inorder to balance the seesaw?

Answer 1

We have the next information

The moment of a force about the fulcrum is equal to the balance of the seesaw so in order to know the moment of force on both sides of the fulcrum must be the same in order to balance.

so we have the next equation

`m1\cdot g\cdot d1=m2\cdot g\cdot d2`

m1=mass one

m2=mass two

d1=distance 1

d2 distance 2

in our case we have

m1= 40 kg

d1=2m

m2=30 kg

d2=?

we substitute the values given in the formula above

`(40)(9.8)(2)=30(9.8)(d2)`

then we isolate d2

`40(2)=30d2`
`d2=(40(2))/(30)=2.67m`

Hence the girl sit 2.67m from the fulcrum