Swinging With Pendulums

Carter Colclasure Period 5

Background Information

Physics is the study of matter and energy and how they interact with each other. Motion, light, electricity, gravity, and radiation are all forms of energy. The goal of physics is to develop scientific theory laws. The stored energy is called potential energy. There are two kinds of potential energy. There are elastic potential energy and gravitational potential energy. Gravitational potential energy stores energy as a result of its elevated position. Like the wrecking ball. Elastic potential energy is the energy as a result from the materials elasticity or compression. It is like a bow and arrow or a gun. When a spring compresses it holds a lot of energy that is why when it lets go it goes flying.Kinetic energy is the energy of motion. There are many types of kinetic energy for example there is vibrational, rotational, and transitional. We focus on translational kinetic energy. Translational is when an object moves from one place to another thats what we think about when we think about kinetic energy. Kinetic energy depends on the mass and speed of an object.


My purpose in the experiment was to determine how the weight, length, and elasticity of a pendulum effects the period and duration.


If I change the weight, length, and elasticity of a pendulum then the average period and duration will increase because the longer the string is the longer the time will be.

Parts of Experiment

Dependent Variable- the period and duration of the pendulum

Independent Variable- the weight, length, and elasticity of a pendulum

Control Group- a one foot long string with 1 washer pendulum

Experimental Group- Group B, C, D, and E will all have their weight, length, or elasticity changed

Factors Held Constant- The point from where I dropped the pendulum from and, the same type of washers.


  • 3 yards of string

  • 5 rubber bands

  • 5 washers

  • 1 stopwatch

  • 1 1 yard dowel

  • 2 of the same chairs

  • 1 scissors


1. Set two chairs of the same next to each to each other

2. Put the dowel on top of the chairs

3. Tie 1 foot string to the dowel with 1 washer on the bottom.

4. Swing it from horizontal position. Record the time of the period and duration

5. Do the same thing but have a 2 foot string

6. Have one 1 foot with 2 washers and swing it. Record the Period and duration

7. Cut on rubber band lay it out and measure it.

8. Cut the same length of string

9. Tie one washer to the rubber band and the other side to the dowel and swing. Record the period and duration

10. Do the same thing for the string

Observations and Data

  • The observations and data were very clear. I observed that the longer the string of a pendulum is the longer the period was. Because the string is longer the pendulum bob has to swing a longer distance which is why the time it takes to swing back and forth is longer. Also I discovered that the weight of the bob greatly affected the period and duration of the pendulum. The greater the weight the faster the pendulum will swing. And finally I made the conclusion based on my data that the elasticity of a pendulum has a very little effect of the swing.

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For my calculations I did a ttest on my data. A ttest compares data and finds the probability. For the first test I compared the first groups average that has a 1 foot string and 1 washer’s period and the group with the 2 foot string and 1 washer. The p value (probability) was 5.185E-07. The second test I compared the control and the group with the a 1 foot string and 2 washers periods. The p value was 0.0013007. Also I compared the rubber band with a washer and the string the same length as a rubber band. The p value was 0.5346958. Then I compared the total duration of group 1 and group 2. The p value was 1.22848E-11. After that I compared group one and group three. The p value of that was 1.46381E-13. Finally I compared group 4 and 5, the p value was 0.340532494.


The trends were very obvious in my experiment. I observed that the longer the string of the pendulum is the longer the period is. Although the period is longer when the string is longer the total duration of the pendulum is significantly shorter. In the experiment I discovered how the weight of the pendulum bob affects the period and duration. The weight of the bob did not have much effect on the pendulum, but it did make the period a little faster. Also the weight greatly changed the total duration. I also experimented to find out how does the elasticity affects the pendulum. I observed that the elasticity of the pendulum does close to no effect on the pendulum at all. The average period for the pendulum with a one foot string and one pendulum was 1.36 seconds and the average for the pendulum with a two foot string is 1.79 seconds. This shows that the string does make the period longer. The average duration for the one foot one washer was 84.43 seconds. The longer string was 50.38 seconds, a significant change. Group C, one foot string with two washers, had an average period of 1.27 seconds and a duration of 48.92 seconds. The period is slightly faster than the pendulum with one washer and the duration was about 40 seconds less than the one washer pendulum. The rubber band with one washer had an average period of .78 seconds and an average duration of 37.2 seconds. I cut a string the same length as the rubber band so the two could be compared. The average period was .79 seconds and duration was 36.66 seconds. The two groups numbers were very close so i concluded that the elasticity does not have much effect of the pendulum. The reason that when the string is longer and the period is longer is because that there is a longer path that it has to swing. The duration is shorter because during the long swing the pendulum loses energy quicker which makes it stop a lot faster. The reason that the period is faster when there is more weight is simply gravity. When it is heavier it drops faster.


My hypothesis was partially correct I thought that every variable I changed the time would increase. I was correct when I changed the length of the string the period increased but the duration didn’t the duration went faster. I was wrong about the weight. The weight made the period and duration go faster. I was not right nor wrong about the elasticity. The elasticity made no effect at all on the pendulum.

Sources of Error and Inaccuracy

As always mistakes are made. In my experiment the times could have been a little of. I tried to drop the pendulum all from the horizontal position, but they all were not probably dropped from the exact same spot. Also on the period i had to eyeball it and see when it made it back to horizontal position and stopped the timer. The time was not always stopped at the perfect time.


In some clocks there are pendulums and the people making the clocks need the period to be exactly two seconds long so the clock will stay on the right time. They need to know exactly how the weight, length, and elasticity have effect on the pendulum so they can have the clock working properly.

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I could improve my design of my experiment by buying an actual pendulum set instead of making my own from dowel rods, string, and washers. If in the future I wanted to continue my research I could see how the string, weight, and elasticity affects the velocity of the pendulum.


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