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.