Fluid and Tension?

Question

An empty rubber balloon has a mass of 0.0120 kg. The balloon is filled with helium at a density of 0.181 kg/m3. At this density the balloon is spherical with a radius of 0.300 m. If the filled balloon is fastened to a vertical line, what is the tension in the line?

Answer 1

Tension is the difference due buoyancy and weight of the balloon

T=g[V(p(He) - p(air))-m(balloon)]
V- voluem of the balloon
p(He)-density of helium [0.181 kg/m3]
p(air) -density of air [1.2 kg/m3 ]
g - acceleration due to gravity

T=9.81[4/3 pi (0.300)^3(1.2 -0.181 ) - 0.0120]= 1.01N