# Homework Help: Balloon Thread Height

1. Feb 29, 2016

### vinamas

1. The problem statement, all variables and given/known data
A heluim filled spherical balloon with a radius of 40 cm got tied into a uniform thread (uniform density) the threads length is 2 meters and its mass is 50 g the balloon ascends when left and ascends a the thread for h meters before it stabalizes again given the empty balloon's mass of 250 g and the density of is 1.29 kg / m^3 and heluim's density of 0.179 find h.

2. Relevant equations
I dont really know but I think we need to use Fb and pressure(pascal)

3. The attempt at a solution

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2. Feb 29, 2016

### Staff: Mentor

Correct assessment so far. What is the mass per unit length of thread? If the thread is h meters long, what is the mass of the thread?

3. Feb 29, 2016

### vinamas

50 grams as I stated

4. Feb 29, 2016

### Staff: Mentor

You stated that, if its length is 2 meters its mass is 50 grams, and I asked, if its length is h meters, what is its mass. Do you see the difference???

5. Feb 29, 2016

### vinamas

Sorry I might have not been clear but 50 grams is the entire thread's mass and the only one give for the thread the problem doesnt give the mass for the length h

6. Feb 29, 2016

### Staff: Mentor

The first step in solving this problem is to determine from the information given what the mass of the string is if its length is h, rather than 2 meters.

7. Feb 29, 2016

### vinamas

I cannnot seem to find a way to do that

8. Feb 29, 2016

### Staff: Mentor

If 2 meters of the thread has a mass of 50 grams, what is the mass per unit length of thread (in grams per meter)?

9. Feb 29, 2016

### vinamas

25?

10. Feb 29, 2016

### Staff: Mentor

Good. Now, if the mass per unit length of the thread is 25 gm/m, and the length of the thread is h meters, what is the mass (in grams) of the thread (algebraically, in terms of h)?

11. Feb 29, 2016

### vinamas

25 per m-h?

12. Feb 29, 2016

### Staff: Mentor

It's 25h grams. So, if h = 2 m, for example, the mass is 50 gm, and if h is 12 m, the mass is 300 gm. Does that make sense now?

13. Feb 29, 2016

### vinamas

yes but how do I find h ?

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