Phy 105/02 Fall 2003
Lab Group 77 (Group Members: Lennon/DiDio/McCartney)
Lab Date: September 2, 2003
Lab Report Submittal Date: September 9, 2003
Lab 1: The Pendulum
Abstract
The goal of this experiment was to determine the effect of mass and length on the period of
oscillation of a simple pendulum. Using a photogate to measure the period, we varied the
pendulum mass for a fixed length, and varied the pendulum length for a fixed mass. The results
of this experiment are in close agreement with theory: mass had no measurable effect on the
period of our pendulum, while the data for period vs. length is well-described by a power-law
relationship close to the theoretical square-root dependence.
Introduction
Theoretically, the period of a pendulum is independent of its mass, and depends on length
according to the power-law relationship
TL∝
where T is the period of oscillation and L is the length. This result can be determined using a
dimensional-analysis approach. The independence of mass is a result of the fact that all objects
are accelerated towards the center of the earth with the same acceleration of gravity.
Procedure/Data Analysis
A mass was attached to a string and suspended from a ring stand. A piece of paper with an angle
drawn on it was used to start the pendulum from the same initial angle for each measurement.
The pendulum swung through a photogate timer connected to a PASCO interface box, and data
was collected using Science Workshop
All data collection started a few seconds after the pendulum's release, allowing the pendulum to
settle down into a regular motion. The pendulum was allowed to swing through 4-6 oscillations.
Scientific Workshop was used to calculate the average period of oscillation. These periods were
then recorded for a set of different masses for the same length of string, and then for a set of
different string lengths for the same mass.
Mass variations
For this part of the experiment the length was fixed at 0.6 m.
mass (g) T (s)
50 1.56
100 1.59
250 1.56
375 1.57
400 1.56
