PhysicsName: ______
Hot Air Balloon After-Flight Analysis
Purpose: to determine the temperature of the hot air in your balloon. You will do this by finding the density of the hot air in your balloon and comparing that density to a table of density vs. temperature. This information will be added to a class database that will allow us to estimate the temperature that a balloon will reach, given its volume.
Directions:
1) Finding Your Balloon’s Actual Volume: When it is set on “2,” the blue “air source” puts out about 0.004m3 of air per second. Squeeze all of the air out of your balloon. Then time how long it takes the air source to inflate your balloon on the number 2 setting. Make sure that you seal completely around the air hose. To get balloon volume, multiply seconds of inflation by the fill rate of 0.004m3/second.
Time to inflate balloon = ______sVolume of Balloon = ______m3
2) Finding Your Balloon’s Empty Mass (no air): Again, squeeze all of the air out of your balloon. Find the balloon’s mass by putting it on a balance. This will give you the mass of the empty balloon. The mass will be in grams. Divide by 1000 to convert that mass to kilograms
Balloon Empty Mass (no air) = ______g = ______kg
3) Finding The Mass of Rope Lifted: We need to know the mass of rope that your balloon lifted. Each cm of rope has a mass of 0.14g. To get the total mass of rope lifted by your balloon, multiply the length of rope lifted (in centimeters) by 0.14g/cm. This will give you the rope mass in grams. Divide by 1000 to get kilograms.
Length of rope lifted = ______cmMass of rope lifted = ______g = ______kg
4) Finding the Overall Mass Of Your Balloon (including rope and hot air): We can find this overall mass because we know the overall density of your Balloon+rope+hot air. Remember that, after the rope was attached to your balloon, the balloon hovered in place. To be more accurate, the Balloon+rope+hot air hovered in place. It wasn’t rising, and it wasn’t sinking. This means its density must have been exactly the same density as the air around it. The surrounding air density was about 1.2kg/m3, so the density of the balloon+rope+hot air must have been 1.2kg/m3. We know the volume of the balloon from #1, above. We also know that density = mass/volume. We can rearrange the density formula to solve for mass; mass = density x volume. Use this formula to find the overall mass of the balloon+rope+hot air.
Density = 1.2kg/m3volume = ______m3Overall Mass = ______kg
5) Finding the mass of the hot air in your balloon: In #4 you found the total mass of your balloon+rope+hot air. In # 3 you found the mass of the rope. In #2 you found the mass of the empty balloon. Now you can find the mass of the hot air in the balloon. Substitute what you know into the following equation, and then solve for hot air mass. Make sure all of your masses are in kilograms…
Total mass = empty balloon mass + hot air mass + rope mass.
Hot air mass = ______kg
6) Finding the density of the hot air in your balloon: density = m/v. Search through your previous answers for the mass and volume of the hot air in your balloon. Then calculate the density of your balloon’s hot air. Note that the hot air volume is the same as the balloon volume.
Density (kg/m^3) / Temperature (F)1.090 / 125
1.081 / 130
1.072 / 135
1.063 / 140
1.054 / 145
1.046 / 150
1.037 / 155
1.029 / 160
1.020 / 165
1.012 / 170
1.004 / 175
0.996 / 180
0.989 / 185
0.981 / 190
0.974 / 195
0.966 / 200
0.959 / 205
0.952 / 210
0.945 / 215
0.938 / 220
0.931 / 225
0.924 / 230
0.918 / 235
0.911 / 240
0.905 / 245
0.898 / 250
0.892 / 255
0.886 / 260
0.880 / 265
0.874 / 270
0.868 / 275
0.862 / 280
0.856 / 285
0.850 / 290
0.845 / 295
0.839 / 300
Hot air mass = ______kgHot air volume = ______m3
Hot air density = ______kg/m3
7) Use the table on the right to determine the temperature of your
balloon’s hot air. Temp = ______F
8) Summary of Data: Transfer some data from the previous questions to the table below.
Time to Inflate Balloon -- from #1 (s)Empty Balloon Mass -- from #2 (g)
Length of Rope Lifted -- from #3 (cm)
Balloon Volume – From #1 (m3)
Overall Mass -- from #4 (kg)
Hot air Mass -- from #5 (kg)
Hot air Density -- from #6 (kg/m3)
10) Comparison of Actual Values to Predicted Values:
A. Before you made your balloon, you created a box-shaped design. What was the predicted volume of your box-shaped design? If it is different from your actual balloon volume, what do you think accounted for that difference?
Predicted volume = ______m3Actual Volume = ______m3
Reason for difference:
B. What was the predicted mass of your box-shaped design? If it is different from your actual balloon empty mass, what do you think accounted for that difference?
Predicted empty mass = ______m3Actual empty mass = ______m3
Reason for difference: