Posted by lou on .
3 point mass of 4g placed at x=1,3,6. where should a point fourth mass of 4 gm be placed to make the center of the mass at the orgin?
this what i got : 24+4+12+4x/16=8+4x/16. this what i did but i didn't get the right answer(which is 2) can someone tell me what is the problem

center of mass 
sean,
to find the center of mass, you add up all of the xpoints * all of their corresponding masses. (e.g. sum x*m)
and you divide it by the sum of all of the masses (e.g. sum m)
therefore (sum x*m)/(sum m).
you are looking for where to place x to make the center of mass at the origin.
so (1*4)+(3*4)+(6*4)+(x*4) = 0
solve for x.
8 = (x*4)
x = 2
TahDah!!