A 100kg weight is placed 0.75 meters from a see-saw on the right hand side. Dan is 75kg. How far away does he have to sit from the pivot on the left hand side to have it balance?

A see-saw represents a pivot, for the see-saw to balance the moment on the left hand side has to equal the moment on the right hand side. Moment =  Force * distance Therefore the moment of the right hand side is 100kg * 10N/kg * 0.75m = 750N/m The moment of the left hand side is 75kg10N/kgdistance. So the distance = 750/(75*10) = 1 meter.