Designing a Pendulum
Patty Gordon

Three groups of physical science students designed an experiment to see what factors changed the swing time (or period) of a pendulum. Each group tested a different variable:

Group 1 – weight of bob
Group 2 – height of drop
Group 3 – length of string

The groups constructed their pendulum. During the experiment Group 2 had a hard time with the protractor to record the height of the drop, so they just “eye-balled” the height each time. They also had a difficult time with the 85-centimeter-long string so, after 2 trials, they shortened the string to 25 centimeters.

To determine the period of the swing, the groups divided the time recorded in seconds by 10. They repeated this procedure each time they manipulated the independent variable for their group. At the end of the period the groups shared their data. Group data is recorded in the tables that follow.

Group 1 – weight of bob
Weight of bob
(grams) Time for 1 period
(seconds)
10 g 2.14 s
20 g 2.18 s
30 g 2.09 s
40 g 2.20 s
50 g 2.18 s

Group 2 – height of the drop
Height of the drop
(degrees) Time for 1 period
(seconds)
20 degrees 1.80 s
30 2.78 s
40 1.27 s
50 1.55 s
60 2.06 s

Group 3 – length of the string
length of the string
(cm) Time for 1 period
(seconds)
85 1.98 s
70 1.74 s
55 1.51 s
40 1.28 s
25 1.04 s

Question
What would not be an acceptable hypothesis for this experiment?
Responses
A The period of a pendulum is directly proportional to the weight of the pendulum’s bob.The period of a pendulum is directly proportional to the weight of the pendulum’s bob.
B The period of a pendulum is directly proportional to the height of the dropped pendulum.The period of a pendulum is directly proportional to the height of the dropped pendulum.
C The period of a pendulum is directly proportional to the length of the pendulum’s string.The period of a pendulum is directly proportional to the length of the pendulum’s string.
D The period of a pendulum is directly proportional to the force of the initial push on the pendulum.

Question

Designing a Pendulum
Patty Gordon

Three groups of physical science students designed an experiment to see what factors changed the swing time (or period) of a pendulum. Each group tested a different variable:

Group 1 – weight of bob
Group 2 – height of drop
Group 3 – length of string

The groups constructed their pendulum. During the experiment Group 2 had a hard time with the protractor to record the height of the drop, so they just “eye-balled” the height each time. They also had a difficult time with the 85-centimeter-long string so, after 2 trials, they shortened the string to 25 centimeters.

To determine the period of the swing, the groups divided the time recorded in seconds by 10. They repeated this procedure each time they manipulated the independent variable for their group. At the end of the period the groups shared their data. Group data is recorded in the tables that follow.

Group 1 – weight of bob
Weight of bob
(grams)	Time for 1 period
(seconds)
10 g	2.14 s
20 g	2.18 s
30 g	2.09 s
40 g	2.20 s
50 g	2.18 s
 
Group 2 – height of the drop
Height of the drop
(degrees)	Time for 1 period
(seconds)
20 degrees	1.80 s
30	2.78 s
40	1.27 s
50	1.55 s
60	2.06 s
 
Group 3 – length of the string
length of the string
(cm)	Time for 1 period
(seconds)
85	1.98 s
70	1.74 s
55	1.51 s
40	1.28 s
25	1.04 s

Question
What would not be an acceptable hypothesis for this experiment?
Responses
A	The period of a pendulum is directly proportional to the weight of the pendulum’s bob.The period of a pendulum is directly proportional to the weight of the pendulum’s bob.
B	The period of a pendulum is directly proportional to the height of the dropped pendulum.The period of a pendulum is directly proportional to the height of the dropped pendulum.
C	The period of a pendulum is directly proportional to the length of the pendulum’s string.The period of a pendulum is directly proportional to the length of the pendulum’s string.
D	The period of a pendulum is directly proportional to the force of the initial push on the pendulum.