Name______Date______Period______

SWING TIME – Pendulum Lab

Objective: Take a swing at making a simple pendulum that demonstrates potential and kinetic energy.

Part I - Make a Prediction:

·  Will increasing the mass of a pendulum affect the amount of times it swings back and forth in 15 seconds?

·  What happens to the potential energy of a pendulum if you increase its mass?

Part II - Procedure:

1)  Get the following materials: 5 Metal Washers, 1 Pencil Pendulum, 1 Timer

2)  Tape the pencil pendulum to a desktop so that the pendulum half extends off the desk.

3)  Slip one washer onto the paper clip. Pull the paper clip so that the string is parallel with the desktop. Then release it. Partner 1 keeps time while partner 2 counts the number of swings in 15 seconds. Repeat for two more trials.

4)  Add a second washer to the paper clip. Repeat step 3.

5)  Continue until you have completed three trials each with one, two, three, four, and five washers.

6)  Calculate the average (mean) number of swings for each amount of washers.

Part III - Data:

Number of Swings in 15 Seconds
# Washers / Trial 1 / Trial 2 / Trial 3 / Average
1 / swings / swings / swings / swings
2 / swings / swings / swings / swings
3 / swings / swings / swings / swings
4 / swings / swings / swings / swings
5 / swings / swings / swings / swings

Part IV - Calculations:

·  Calculate the potential energy for each of the different pendulum masses that you used in the experiment using the following information. Measure the height as distance from the paperclip to the floor at start.

# Washers / Total Mass / Potential Energy
1 / kg / Joules
2 / kg / Joules
3 / kg / Joules
4 / kg / Joules
5 / kg / Joules

Part V - Conclusion:

1.  Did increasing the mass make a major difference in the number of swings in the 15 seconds? Why do you think this is the case?

2.  Did increasing the mass change the amount of maximum potential energy of the pendulum? Explain.

3.  Did increasing the mass change the amount of maximum kinetic energy of the pendulum? Explain.

4.  What energy conversion keeps taking place as the pendulum swings back and forth?

5.  Label the diagram below to show the area of highest kinetic energy. Why did you choose that location?

6.  Label the diagram above to show the areas of highest potential energy. Why did you choose those locations?

7.  Why does the pendulum eventually stop swinging? Where does the energy go?

8.  Does this lab demonstrate the Law of Conservation of Energy? Explain why or why not.

9.  Challenge Question: What do you think a perfect pendulum would do over time if there was no friction?