“Great Hovering Helium Balloons, Batman!” Lab

** **

**Objective:**
Use the following information about air and helium to determine how many
paperclips (fractions of paperclips is acceptable – eg. 38.75 paperclips) it
will take to make a helium balloon just hover in mid-air.

**It is forbidden:**
It is forbidden for you to hang any paperclips on the balloon until you
show me your calculations for the number of paperclips you will need.

**Information:**

r_{air}
= 1.29 kg/m^{3} at 0^{o}C and 1.18 kg/m^{3} at room
temp (25^{o}C)

r_{helium
}= 1.78 x 10^{-1} kg/m^{3} at 0^{o}C and 1.63 x 10^{-1} kg/m^{3} at
room temp (25^{o}C)

**Helpful hints:**

1. Try to make your balloon as spherical as you can so that you can determine its volume more easily.

2. Barring that, you can take several measurements of the circumference of your balloon and find an average volume.

3. When you go about
finding the mass of a single paperclip, it is better if you find the mass of 20
or 30 of them and divide by that number to find the **individual**
mass. Most paperclips are the same
mass, but you get a better “average” by doing it this way.

4. You might want to tie a string to your balloon to keep it attached to a ring stand or something while you work out the calculations. Be sure to either cut off your string before you hang paper clips or to include it in the mass of the balloon.

**What is due for this lab:**

1. Write up a procedure of how you went about doing this lab.

2. Write up a data table of all of the data you collected for this lab.

3. Write up a calculation section of all of the calculations you needed to do. Put the calculations in order such that they go in the order of the data table.

4. Answer these questions:

1. How many helium balloons would it take to lift you off the ground.

(0.22 lbs = 1 N)

2. What is the net force in the upward direction of your balloon? Find this by

hooking up a force probe and opening Logger Pro on the computer. Tie a string to

your balloon and hook it on the balloon.

3. Determine the percentage error between your
predicted F_{net} and the actual F_{net}

you determined by using Logger Pro.