physics
posted by Anonymous on .
A 82 kg adult sits at one end of a 8.6 m long board. His 23 kg child sits on the other end. Where should the pivot be placed so that the board is balanced, ignoring the board's mass? Find the pivot point if the board is uniform and has a mass of 15 kg. Please help with stepbystep explanation for both parts! Thanks!

notice the mass of the board and loads are (massboard+82+15)
One can start anywhere, let the end with the adult be zero.
Sum moments about that end.
boardweight*4.3+23g*8.6piviotlength*(massboard+loads)=0
lets solve it...
15*g*4.3+23*4.6(massboard+82+23)g=0
the first part lets massboard be zero.
the second part lets it be 15kg.
In either case, solve for L, the position of the piviot point from the adult end. 
Kpmwpmwpu :kgnpg

To many morons who cant explain...