Trixie Le 2nd Period Mr. Sarringhouse 9/16/14 Investigating the Flight of an Elastic Band Lab Problem: To determine if stretching the rubber band to different lengths would change the displacement of the rubber band after its projectile and launch. Background: In order for a rubber band to be launched and have a flight of a certain distance, the factors that help determine this are potential energy, energy that is stored in an object due to its position, and kinetic energy, energy in motion. One prime example of this would the old “snakes in a can.” The snakes are compressed inside the can, which is the potential energy, and when it is released and opened, it flies out, which is due to its potential energy turned to kinetic energy. In the mechanical system of the rubber band, stretching the rubber band creates a sort of potential energy that turns into kinetic energy in its projectile. Hypothesis: If the length the rubber band is stretched affects the displacement of the rubber band after projectile, then the distance will change in correspondence to the length that the rubber band is pulled on, because potential energy is converted into kinetic energy in the rubber band’s projectile. Variables: Controlled variables Use the exact same rubber bands Environment o Temperature Ruler for measurement Height of flight Gravity Angle the rubber band was launched Independent variables The rubber band was stretched before launching Dependent variable Projectile and distance of rubber band flight Potential and kinetic energy of the rubber band Materials: A meter stick table Protractor One rubber band
Procedures: Flight of the Rubber band (refer to figure 1) 1. Arrange the two perpendicular meter sticks so that the height of the launch off the ground will remain the same for each trial. 2. Take the rubber band and place the top of it on the Meter Stick A and pull it back at a certain length at a 45 degree angle to the left but leveled to the ground and measure it with a protractor. 3. Release the rubber band and make sure there are no obstructions in the way. 4. Take the trundle wheel and measure the displacement of the rubber band from its initial point of Meter Stick B to the place it landed. 5. Repeat steps 1-4 with pulling the rubber band back 10 centimeters, 15 centimeters, and 20 centimeters. 6. Repeat steps 1-5 and do five trials for the rubber band that is pulled back 10 centimeters, 5 centimeters, and 20 centimeters Figure 1
Meter Stick A
Rubber band
Meter Stick B
Distance of flight
(
Data: Raw Data Flight of the Rubber Band (m)
Stretch Distance
Trial 1
Trial 2
Trial 3
Trial 4
Trial 5
10 cm
1.5 ± 0.05
1.6 ± 0.05
1.6 ± 0.05
1.4 ± 0.05
1.5 ± 0.05
15 cm
3.3 ± 0.05
4.6 ± 0.05
3.5 ± 0.05
4.2 ± 0.05
3.6 ± 0.05
20 cm
6.4 ± 0.05
5.9 ± 0.05
6.2 ± 0.05
6.3 ± 0.05
6.1 ± 0.05
Calculations Finding average displacement of stretch distance 10 cm. 1.5m + 1.6m + 1.6m +1.4m + 1.5m = 7.6 m 7.6 m/5 = 1.52 m 1.6m – 1.4cm = 0.2m/2 = 0.1 cm 1.52 m ± 0.1 m The displacement was bearing 45 degrees north east. Finding average displacement for stretch distance of 15 cm 3.3m +4.6m + 3.5m + 4.2m +3.6m = 19.2 m 19.2m/ 5 = 3.84 m 4.6m - 3.3m = 1.3m 1.3m/2 = 0.65 m 3.84 m ± 0.65m The displacement was bearing 45 degrees north east. Finding average displacement for stretch distance 20 cm 6.4m + 5.9m + 6.2m + 6.3m + 6.1 = 30.9m 30.9 m/5 = 6.18m 6.4m – 5.9m = 0.5 cm 0.5 cm/ 2 = 0.25 cm 6.18 cm ± 0.25 cm The displacement was bearing 45 degrees north east.
Processed Data Stretch Distance (cm) 10 cm
Flight of Rubber Band Averages (m)
15 cm
3.84 m ± 0.65m
20 cm
6.18 cm ± 0.25 cm
1.52 m ± 0.1 m
Conclusion: This is experiment was a success overall. This experiment was a success because a correlation was found between the length a rubber band is stretched and its displacement after launching. As the rubber band is stretched, more force is exerted onto the rubber band and the elastic potential energy is increased. Once that potential energy is increased, it converts into kinetic energy when the rubber band is launched. Therefore, rubber bands with higher elastic potential energy, have higher kinetic energy, and go a farther distance. The further the rubber band was stressed, the further it traveled, as seen on the graph. Furthermore, the correlation between the length the rubber band was stretched and its displacement was proven through the following procedures. In order to make sure each rubber band was launched at the same height, a meter stick was utilized. Then, the rubber band was pulled back by the end of another meter stick at a 45 degree angle to the left, still parallel to the ground. In order to measure the distances the rubber band stretched, another meter stick was utilized and it was perpendicular to the first meter stick. These measures were taken so that the variables would remain constant and to obtain the most precise and accurate measurements The distances it stretched were 10 centimeters, 15 centimeters, and 20 centimeters. Five trials were done for each length the rubber band stretched and the averages were calculated. From the five trials, the 10 centimeters stretched rubber band traveled 1.52 m in average, the 15 centimeters stretched rubber band traveled in average 3.84 m, the 20 centimeters pulled back rubber band traveled a distance of 6.18 m in average. Similarly, the uncertainties were accounted for with precision and accuracy for each measurement of the flights. All of these projectiles were in the direction of bore 45 degrees northeast. As the rubber band stretched further, so did the magnitude of its displacement. Even though many steps were taken to insure the most precision and accuracy possible, this lab could be improved in numerous ways. A few areas of weakness that needs to be addressed. First of all, using the ruler as a way of having consistent measurements of stretching the rubber band by pulling it back could have been an issue. This is because sometimes when a person pulls back on a rubber band, they may not be able to pull it back to the exact measurement it needs to be. In order to rectify or improve on this is to have one single person do it rather than multiple different people to have less random error bars. However, there is always the chance consistently error bars when people are used. Furthermore, the rulers were may have not been exactly perpendicular. This is possible because there was no sturdy surface to place the ruler on and there could have been a slight angle on the ruler. This could be improved by having a sturdy surface to put the rulers on next time. Another variable that was not accounted for was air resistance and the wind. Even though this was done in classroom, the door was open and the wind was blowing. That could have easily affected the displacement of the rubber band. In order to fix this type of problem, the doors should be sealed next time to ensure of little air resistance. Lastly, a larger range of distances the rubber band being stretched would have been useful to seeing the further correlation between the rubber band stretch and its displacement.
