1. The problem statement, all variables and given/known data A 1.10 g balloon is filled with helium gas until it becomes a 20.0 cm-diameter sphere. What maximum mass can be tied to the balloon (with a massless string) without the balloon sinking to the floor? Density of Air: 1.28 kg/m^3 Density of Helium gas : 0.18 kg/m^3 Volume of a sphere: V = 4/3*pi*r^3 g = 9.80 m/s^2 2. Relevant equations Buoyant Force (Fb) = p (density) * V * g Density = mass/volume Fb = Wo = p (density of object) * V (Volume of object) * g 3. The attempt at a solution Fb = Weight of the object + Mg (M is the mass to be solved) (1.23)(4/3*pi*(0.1m)^3)(9.8) = (0.18)(4/3*pi*(0.1m)^3)(9.8) + M(9.8) M = 4.40 * 10^-3kg I am uncertain of whether the buoyant force is the force of air pushing upwards on the balloon, or whether it is the helium gas in the balloon. Nonetheless, I used air as the density to solve for the buoyant force. Another possibility would be that: T = Fb - mg T = (1.23)(4/3*pi*(0.1m)^3)(9.8) - (0.0011kg)(9.8) T = 0.0397 N Therefore mass of the object = 0.0397N / 9.8 = 4.05 * 10^-3 I am doubtful of which solution is correct and if either solution is actually correct. Thank you in advance.