1. The problem statement, all variables and given/known data A block of mass M is attached to a light string. The string passes over a massless, frictionless pulley and is attached to a solid uniform ball of mass 3M. The ball is at rest and completely submerged in a fluid as shown. What is the ratio of the density of the fluid to the ball? 2. Relevant equations Fb = (rho)Vg Fg = mg 3. The attempt at a solution The forces acting upward must balance the forces acting downward on the ball. Thus, Fb + Tension = Fg Then, (rho)Vg + T = 3Mg We know that the tension in the string is equal to M because it is keeping the block at rest. Thus, (rho)Vg + Mg = 3Mg (rho)Vg = 2Mg Divide both sides by Vg and we obtain: (rho(fluid)) = 2(rho(ball)) This is not the correct answer. Can someone explain what I'm doing wrong?