EXPERIMENT 8.1
ENERGY OF A RUBBER BAND
Student Information:
PURPOSE:
To investigate the elastic potential energy and kinetic energy of a rubber band.
MATERIALS:
- 1—5 rubber bands (all must be the same thickness and length)
- A metric ruler
- Tape measure (one with metric units on it would be best)
- Masking tape
- Safety glasses or goggles
SAFETY:
- Make sure to never point the rubber band at anyone!
- Always wear safety glasses or goggles during this experiment.
- Conduct this experiment in an open area where the rubber band won't hit anything fragile.
- Be careful when retrieving rubber bands to avoid tripping or falling.
BACKGROUND:
It would be best to do this experiment outside or in a long hallway because the rubber band will fly some distance. Make sure to never point the rubber band at anyone! You may also want a helper to help you spot and mark where the rubber band lands as sometimes it will bounce a bit.
When you stretch a rubber band, you are storing elastic potential energy in it. This is a form of potential energy that is stored in elastic materials when they are deformed. The more you stretch the rubber band, the more potential energy is stored.
When you release the rubber band, this potential energy is converted into kinetic energy - the energy of motion. The rubber band flies through the air because of this kinetic energy. The relationship between how much you stretch the rubber band (the potential energy you store) and how far it flies (the kinetic energy it receives) is what we'll be investigating in this experiment.
QUESTIONS:
What is the relationship between the potential energy of a stretched rubber band and its kinetic energy once the rubber band is released? In other words, how will the potential and kinetic energy of a stretched rubber band affect the distance it travels?
HYPOTHESIS:
Write what you predict will happen to the rubber band (how far will it travel when released) when it is stretched to different lengths:
PROCEDURE:
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Locate a long straight area to conduct your experiment. A driveway or sidewalk on a nice day is perfect. If that is not an option, choose a room that has a long, unobstructed area for you to shoot the rubber band. Select a starting spot and mark it with a strip of masking tape.
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With your feet behind the masking tape line, hook the rubber band over the front edge of the metric ruler and stretch it back to the 10 cm mark on the ruler. Keep the ruler level and let the rubber band go.
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If you have a helper, have them place a masking tape mark where the rubber band lands and return the rubber band to you. If you don't have a helper, you will need to mark the landing place and retrieve the rubber band. (You may also use other rubber bands as long as they are the same thickness and length.)
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Repeat steps 2—3 four more times for a total of 5 trials stretching the rubber band to 10 cm.
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With the tape measure, measure the distance in centimeters from the starting line to the landing point for each of the 5 trials. Record these distances in your data table. Pick up the masking tape marks after recording the distance.
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Repeat steps 2—5, but stretch the rubber band on the metric ruler to 15 cm.
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Repeat steps 2—5, but stretch the rubber band on the metric ruler to 20 cm.
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Repeat steps 2—5, but stretch the rubber band on the metric ruler to 25 cm.
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Average your distances for each stretch length by adding the distances together and then dividing by 5. Record the average in your data table.
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Make a graph of your results by putting the stretch length (in cm) on the x-axis and the average launch distance (in cm) on the y-axis. Plot your data points. What trend do you notice? Do your data points look like they form a straight line? If so, draw a line of best fit.
DATA COLLECTION:
| Stretch Length (cm) | Trial 1 Distance (cm) | Trial 2 Distance (cm) | Trial 3 Distance (cm) | Trial 4 Distance (cm) | Trial 5 Distance (cm) | Average Distance (cm) |
|---|---|---|---|---|---|---|
| 10 | ||||||
| 15 | ||||||
| 20 | ||||||
| 25 |
GRAPH:
Use the interactive graph below to plot your results, or create your own graph on paper.
Stretch Length (cm) vs. Average Launch Distance (cm)
CONCLUSION:
What do your results show? What trend did you see on your graph? What does this tell you about the relationship between potential energy and kinetic energy? Write a paragraph explaining what you found and make connections to what you learned in the text.
ANALYSIS QUESTIONS:
1. Based on your graph, what is the relationship between the stretch length and the distance the rubber band travels?
2. How does the potential energy of the rubber band change as you stretch it further?
3. What happens to the potential energy when you release the rubber band?
4. What factors might affect the accuracy of your experiment?
5. How could you improve this experiment to get more accurate results?
EXTENSION ACTIVITIES:
Try these additional activities to further explore energy conversion:
- Try the experiment with rubber bands of different thicknesses. How does the thickness affect the distance?
- Investigate how the mass of the rubber band affects the distance it travels by attaching small weights to the rubber band.
- Design an experiment to measure the efficiency of the energy conversion from potential to kinetic energy in the rubber band.
SUBMIT YOUR RESULTS:
Click the button below to submit your experiment results to your teacher.