Motion Project: Balloon Rockets
Objective:
What is the effect of using different types of string on the velocity of a balloon rocket?
Materials:
Balloon
Straw
Tape
Cotton string
Waxed dental floss
Stopwatch
Tape measure
Hypothesis:
If a balloon rocket is constructed with cotton string and waxed dental floss, then the velocity of the rocket will be faster with the waxed dental floss.
Safety Precautions:
Ö Be careful not to pop balloon in the face or while in mouth.
Ö Small pieces of broken balloon are a choking hazard.
Ö Do not leave balloons in reach of small children or pets.
Procedure:
1. Tie/attach one end of cotton string to a fixed object.
2. Thread the straw through open string end.
3. Tie/attach the other end of string to another fixed object across the room.
4. Measure the distance from rocket start position to the expected end point. Record distance in meters on the data table.
5. Blow up the balloon several times and release air to loosen elasticity a bit.
6. To begin first trial, blow up balloon. Do not tie shut.
7. Holding the balloon opening firmly, tape it to the straw.
8. Position the balloon rocket in a starting position.
9. Release the balloon and start the stopwatch time.
10. Stop the time when the rocket reaches the measured end point. Record the time in seconds on the data table.
11. Repeat steps 6-10 for two additional trials on the cotton string.
12. Calculate the average time for three trials. Record average time on data table.
13. Calculate and record the average velocity using the formula v = d/t.
d = distance in meters t = average time
14. Repeat the above procedure (steps 1-13) using waxed dental floss.
Data/Observations/Calculations:
String
Type / Distance (m) / Time (s)Trial 1 / Time (s)
Trial 2 / Time (s)
Trial 3 / *Average
Time (s) /
**Velocity
(m/s)Cotton / 6 / 2.70 / 2.75 / 2.68 / 2.71 / 2.21
Dental floss / 6 / 1.42 / 1.63 / 1.50 / 1.52 / 3.9
* Average Time = Trial 1 + Trial 2 + Trial 3
3
**Velocity = Distance_
Average Time
Conclusions:
The purpose of this project was to demonstrate how a variable affects the motion of an object. I chose to construct a balloon rocket, testing how different types of string could slow down or speed up its velocity. The independent variable, therefore, was the type of string, and the dependent variable was its velocity. In order to compare velocities, I had to measure the distance the balloon rocket traveled and the time it went that distance. With this information I was able to use the formula v = d/t to calculate and compare the velocities of two different strings.
The two types of string that I used were cotton string and waxed dental floss. My hypothesis was that the waxed dental floss would have a faster velocity due to less friction between the string and the straw. After three trials with each string, my hypothesis was proved to be correct. Using the average time for each type of string, the velocity of the cotton string was 2.21 m/s. The dental floss, however, was a higher velocity at 3.9 m/s.
Doing this experiment showed that friction is one factor that can affect the velocity of an object. There were other variables in my procedure that may have caused some error in the data. In blowing up the balloon I may have had varying amount of air for each trial. The volume of air that inflated the balloon would have been difficult to measure in order to get a consistent amount each time. I also used the same balloon for each trial. The elasticity of the balloon decreased each time, causing decreased pressure pushing the air out the opening. This could have also affected the velocity of the balloon rocket. I could have tried some other types of string to get a broader idea of the amount of friction that can slow down the rocket. I have learned that there are many factors that can affect the movement of objects.