posted by bob .
A 5 m long see saw has a child whose mass is 25 kg sitting on one end. How far in meters from the center should a 70 kg adult sit on the opposite side for the see saw to balance?
Let A = the child and B = adult person.
To balance this beam, the moment of the right hand side (B) must equal the moment of the left hand side (A).
M(A) = M(B)
m(A)*g*2.5 = m(B)*g*d(B)
62.5 = 70*d(B)
=> d(B) = 70/62.5 = 1.12m
I hope this will help