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Touchme

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## Homework Statement

A helium-filled balloon at atmospheric pressure is tied to a 3.1 m long, 0.100 kg string. The balloon is spherical with a radius of 0.40 m. When released, it lifts a length (h) of the string and then remains in equilibrium as in Figure P9.78. Determine the value of h. When deflated, the balloon has a mass of 0.25 kg. (Hint: Only that part of the string above the floor contributes to the load being held up by the balloon.)

## Homework Equations

P2 = P1 + dg(y1 - y2)

d = density

## The Attempt at a Solution

First I determine the pressure of the balloon by using P = mg/A, and I got 4.874 Pa

Then I use the equation P2 = P1 + dg(h)

4.874 = (0) + (1.29)(9.8)(h). The 1.29 is density of air.

I have no idea why I set p1 equal 0.

The answer I got is wrong and I am stuck. Help please.