# period of the pendulum

Class Exercise 3/Worksheet 3

1. State one of the two major hypotheses the epidemiological study was testing.
1. How many study subjects were recruited for the study?
1. Do you see any differences between the high and low exposure groups participating in the study? Use age and BMI to explore the data from the SPSS file.
1. Do you see any differences in neurobehavioral functions between the high and low exposure groups participating in the study? Use data for any two tests from the SPSS file.
1. When our sample of 50 adolescent children were followed-up after 3 years of the initial data collection to collect new data regarding intellectual disability the study became:
1. A case-control study
1. An experimental study
1. A cohort study
1. Is there an association between child abuse and suicide attempts among chemically dependent (e.g. drugs or alcohol) adolescents using the data presented in the following 2×2 table? Interpret the RR.

RR= (A/(A+B)) / (C/(C+D))

1. Using your own SPSS dataset calculate if there is an association between arsenic exposure in childhood and post-adolescence intellectual disability among the study participants.
1. Calculate RR
1. What are the potential confounding variables that can affect the association between arsenic exposure in childhood and post-adolescence intellectual disability? Mention any two and justify.
1. Have you understood the crossover study design (see the lecture slides on experimental studies)?
1. Yes
1. No
• In a sentence state why, the researchers followed a crossover design.

Examining the Pendulum Materials List

To complete this activity, you will need:

– string or yarn, at least 3-4 feet long

– objects that are identical, so you can add mass to your pendulum

– scissors

– protractor or angle app for your phone (such as Protractor or Angle Pro)

– stopwatch, or the one on your phone

– at least 1 helper, 2 will be better

For this activity, you’ll be making your own pendulum at home! You will be able to test three variables you tested in the lab (mass, angle and length of string), but not gravity. Unless you have your own gravity-free room or access to a space shuttle…

Remember, a pendulum looks like the photo below. A string will hang from a central point, and a mass (or bob) will hang at the end of the string. Your pendulum should be able to swing back and forth without hitting any obstacles.

A simple pendulum is basically a string with a mass tied to the end that can swing back and forth. The time it takes to travel back and forth one time is called the period of the pendulum.

Your job is to design three experiments that test how the following factors affect the period of a simple pendulum. Each time you test a new variable, you will be testing the independent variable. Remember waaaay back to the Scientific Method Lab, the independent variable is the one you change. Remember to only test one independent variable at a time!

First, you must build your pendulum. This site gives some great ideas, and you can always search for more online!

Your three independent variables are as follows:

1) Mass of the bob (Use identical objects to add mass to your bob. Tie them all together in the same spot at the end of the string, do not make them into a “chain of objects”.)

2) Angle of release from vertical (This means the angle you lift it from where it was when it was hanging straight down.)

3) Length of the pendulum (Length of string from the top of the bob to the pivot/attachment point.)

L1: Intuitively, what basic results do you expect from each of the experiments? Consider the results you got from the Gizmo, disregarding the gravity variable.

When designing your experiments keep in mind the sample size and range. You will want to perform more than one trial for each data point. You will want to test a wide range of values for your independent variable, at least three different points. For instance, you should use at least three different masses, three different angles and three different lengths of string.

You will also want to collect enough data points to be able to characterize trends within your data effectively. We have included a data table on the following page to collect your data. You should do each variable at least 10 times, stopping the stopwatch after each period. You will then add up the total time and divide by 10 to get an average.

L2: Why do you think it is necessary to collect so many data points?

L3: Why do you have to stop it each time? Why not just let it go for 10 periods like you did in the Gizmo?

L4: Keep records of all raw data collected during your experiments. Copy the following table into your notebook or copy-and-paste it into a document.

Period of the Pendulum (seconds)

L5: Did you make any adjustments to your plans as you performed your experiments? If so, explain.

Gather your data for the experiment where the mass of the bob was the independent variable.  Using your three masses and their average times, create a graph either on graph paper or in Excel or Word.

Take a photo or screen shot of your graph, making sure your name is clearly visible.

L6:  According to your data, does the mass of the bob have a significant effect on the period of a pendulum?

ather your data for the experiment where the angle of release was the independent variable.  Using your three angles and their average times, create a graph either on graph paper or in Excel or Word.

Take a photo or screen shot of your graph, making sure your name is clearly visible.

L7:  According to your data, does the angle of release have a significant effect on the period of a pendulum?

Gather your data for the experiment where the length of string was the independent variable.  Using your three lengths and their average times, create a graph either on graph paper or in Excel or Word.

Take a photo or screen shot of your graph, making sure your name is clearly visible.

L8:  According to your data, does the length of string have a significant effect on the period of a pendulum?

L9: Gravity on Earth is 9.8 m/s2. How do you think gravity affected your pendulum?

L10:  Is there anything you could have done differently to reduce the effects of gravity?

L11:  What could you do to make your results more consistent?

1. Of your three variables, which one affected the period of the pendulum? Was this consistent with your conclusions from the Gizmo? (2 points)
2. Attach a photo of your three graphs, making sure your name (Farah) is clearly visible on the graphs. (3 points)
3. Describe three factors that influenced the uncertainty in your measurements. Is it possible to do this experiment without uncertainty? (4 points)
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