Investigation: Analyse the Motion of a Pendulum in relation to the mass of the Pendulum
Task:
What are the factors that affect the period swing of a pendulum?
Introduction:
A pendulum can be described in terms of its mass, length, and amplitude. The time
period of a pendulum is the amount of time that a pendulum takes to swing from one peak
to another which is equivalent to one oscillation. In this experiment, mass refers to the
mass of the pendulum bob and it will be the independent variable.
The period swing of the pendulum can be identified a transfer of gravitational
potential energy to kinetic energy and then back. The most fundamental features of a
pendulum are the pendulum bob, the length of the string and the initial gravitational
potential energy. The motion characteristics of the period swing of a pendulum can be
described a relation between gravitational potential energy and the mass of the pendulum
bob. Therefore, it is predicted that the mass of the pendulum bob would affect the period
swing of the pendulum. I predict that with an increase in mass the pendulum would have
more momentum thus the period swing would decrease with more mass.
Design:
Independent Variable:
•
The mass of the pendulum
Dependent Variable:
•
The period swing of the pendulum
Controlled Variable:
•
The length of the string attached to the pendulum bob
o
The length of the string will affect the time period of a pendulum
because depending of the length the oscillation of the pendulum would
differ, for the distance it travels would vary. The piece of string acts as
a radius for the pendulum’s arc, which is similar to a circle.
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o
There would be an increase or decrease in the distance travelled by the
pendulum because according to C=2
r, the circumference of the circle
π
will increase, thus so will the length of length of the arc. Therefore, the
distance travelled by the pendulum varies according to the length of
the string, and therefore the time taken.
o
To control this variable it would be made sure that the length at
which the pendulum is suspended from is measured and kept constant
throughout the experiment. Since a single pendulum with one string
attached to two places is used, for stability and more accuracy, the
suspension of the pendulum bob is measured compared to the length of
the string.
•
The angle from which the pendulum is released
o
The angle from which the pendulum is released is a fundamental
variable which affects the period swing:
1.
Firstly, it increases the length of the arc of the circle. The greater
the angle, the greater the proportion of the circle is taken by the
arc. The amount (arc) that the pendulum swings through is
equivalent to double the value of the angle that it’s dropped from.
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 Spring '10
 Dr.Fleisig
 pendulum bob

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