# Not sure how to start this problem hint please!

An empty rubber balloon has a mass of 0.0135 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?

I don't even know what equation to use...! AHH

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Tide
Homework Helper
HINT: It's a question about buoyancy.

is the tension equal to the force?

lightgrav
Homework Helper
yes, but there are several forces involved here. ...
all dealing with one Volume.

Tide
Homework Helper
Yes. The buoyant force is balanced by the tension in the string.

so would i use the equation B=density(fluid) x volume(fluid) x g?

Pyrrhus
Homework Helper
Yes, substitute it in your $\sum F_{y} = 0$

so it would be Density(Helium) x what volume? x 9.81 ?

mukundpa
Homework Helper
The forces acting on the balloon are gravity force, buoyant force and the tension in the line.

The buoyant force is applied by air of the atmosphere.

Buoyant force is equal to the weight of the displaced volume of the fluid.