Not logged in. Click HERE to login.

This is a virtual version of the second pendulum lab.

In the previous pendulum lab, we built a pendulum, saw how it worked, learned how to make important measurements, and then figured out what determines the period of a pendulum. We figured it out inductively because you looked for a pattern without following a specific experimental procedure. No matter how, somebody could refute that finding and say you did not test all possibilities carefully.

This investigation is heavily based on understanding how variables work in a scientific experiment. Before you start, you should review independent variables, dependent variables, and controlled variables.

Simulation provided by Phet Interactive Simulations.

Link to the simulation

Getting Started

First, simply rebuild the pendulum and review how to set and measure length, mass, amplitude, and period.

Throughout this investigation, we will call length, mass, and amplitude, the input variables, because you directly control them, and we will call period the output variable, because it is determined based on the input variable.

Input Variables
  • Length
  • Mass
  • Amplitude
Output Variable
  • Period

Defining a "Deductive Experiment"

  1. A single deductive experiment consists of a single independent variable, a single dependent variable, and as many controlled variables as necessary.
  2. The experimenter systematically sets the independent variable to a series of different values.
  3. For each value of the independent variable, the experimenter measures the value of the dependent variable.
  4. While changing the independent variable, each controlled variable is set to a constant value and never changed. This ensures that, if there is a change in the dependent variable, it comes from the changes in the independent variable and no other factor.
  5. Based on the results, the experimenter determines if there is a causal relationship between the independent and dependent variables.

The Task

The task here is to conduct three separate deductive experiments using the pendulum. Each experiment must meet the following requirements.

Don't do this!!!

The most common error is mistaking an experiment with a measurement. A single experiment must consist of several measurements.

This complete investigation consists of three separate experiments, each with at least 6 measurements, for a total of 18 measurements.

LAB REPORT FORMAT

Formatting of assignments is crucial because the format should reflect the goal of the assignment. In this assignment, the goal was to design experiments. Therefore, the formatting needs to reflect proper experimental design

3 Sections, Each Describing an Experiment

Your report should be broken into three different sections, each describing one of the three experiments you conducted. Each experiment must be presented as an independent unit, separate from the others. The writeup of each experiment should be as though you didn't even do the other two.

Requirements for Each Experiment Writeup

**I prefer handwritten graphs because I think the process of plotting each point helps you think more clearly about what the points mean. This manual process is lost when a computer creates your graph in an instant.

Example:

Experiment 1
  • Definitions of variables:
    • Independent Variable: ____________________
    • Dependent Variable: ____________________
    • Controlled Variables and Values: ____________________
  • Data Table:
  • Scatter Plot:
  • Analysis:
Experiment 2
  • Definitions of variables:
    • Independent Variable: ____________________
    • Dependent Variable: ____________________
    • Controlled Variables and Values: ____________________
  • Data Table:
  • Scatter Plot:
  • Analysis:
Experiment 3
  • Definitions of variables:
    • Independent Variable: ____________________
    • Dependent Variable: ____________________
    • Controlled Variables and Values: ____________________
  • Data Table:
  • Scatter Plot:
  • Analysis:

Remember that the key to having a good science report is not a long report, but a concise report that clearly organizes information!