Need: Notebook
CLASS Notes:
Pendulum Lab with Clocks
Handouts: Two reading
(no notes)
Two HW sheets
Quiz Monday on pendulum
problems
Start Pendulum clock lab on Monday also
Please Place Papers in the bin. If absent write dates on top
Retake Dates
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See How They Run
Barbie and Ken Lab
Hooke’s Law Quiz
Hooke’s Dry Lab
Reaction time lab
All other tests and quizzes
All other Labs
late -50%
late -20%
Late -50%
Late -50%
Late -50%
Redo by Friday
ONLY Rewrite if NY
ONLY Retake if NY
ONLY Rewrite if NY
Uses of a simple pendulum
• Simple pendulums are used to keep time in
clocks in olden days.
• A simple pendulum is also used to calculate
acceleration due to gravity g at various
places on the earth and above the earth.
History of the pendulum
• The discovery of
oscillatory motion of
a pendulum and its
properties are
attributed to the
famous astronomer
Galileo.
Leaning Tower of Pisa,
• The story goes that as a small child he used to
be taken to a cathedral in Pisa, Italy, by his
parents.
History of the pendulum
The cathedral is
next to the leaning
tower of Pisa.
History of the pendulum
• Child Galileo
was once bored
listening to
sermons in the
cathedral. There
were gas lamps
hanging from
the ceiling of the
cathedral.
History of the pendulum
• Due to the breeze,
the lamps were
swinging from the
ceiling.
History of the pendulum
• Galileo noticed that the
swinging was periodic in
nature by measuring time
from the pulse or heart beats
on his wrist.
History of the pendulum
• He saw that the
swinging lamp came
to its one extreme
position after a fixed
number of beats on
the heart beats on
his wrist.
History of the pendulum
• Galileo later discovered the
detailed the nature of simple
pendulums and their
properties.
Frequency:
Pendulums
Practice Problem on whiteboard
Use your equation sheets
Equation, substitute, solve with label.
1)A kid on a playground swing makes a
complete to-and-fro swing each 2 seconds.
Do not leave
The frequency of swing is _________. answer as a
fraction
glenbrook.k12.il.us
Frequency:
Pendulums
Practice Problem on whiteboard
Use your equation sheets
Equation, substitute, solve with label.
2) A tennis coach paces back and forth
along the sideline 10 times in 2 minutes.
The frequency of her pacing is
Do not leave
answer as a
fraction
________.
glenbrook.k12.il.us
PROBLEM: A man wants to know the height of a building which
has a pendulum hanging from its ceiling. He notices that in one
minute the pendulum oscillates 8 times.
What is the total time, t? 60sec
•What is the frequency?
•f = 8/60
•f=0.13 Hz
or 0.13/sec
•What is the Period, T?
•T=1/f
•T=1/.13
•T=7.5 sec
or 0.13 sec-1
PROBLEM: A man wants to know the height of a building which
has a pendulum hanging from its ceiling. He notices that in one
minute the pendulum oscillates 8 times. What is the height of the
building?
List
T =?
#cycles=8 oscillations
t= 60 s
L=?? (=height of building)
T = time/# cycles
T = 60 sec/8 cycles
T = 7.5 sec
PROBLEM: A man wants to know the height of a building which
has a pendulum hanging from its ceiling. He notices that in one
minute the pendulum oscillates 8 times. What is the height of the
building?
List
T = 7.5 sec
#cycles=8
t= 60 s
L=??
7.52= 4π2 (L/9.8)
7.52= 39.44 (L/9.8)
7.52(9.8)= L
39.44
L = 14.7 m
Now you try a problem.
• The period of a simple pendulum is 2
seconds. Find its length.
= 1 meter
Another problem
A pendulum has a length of 3.0 m
and executes 20. complete
vibrations in 70. seconds.
Find the acceleration of gravity at
the location of the pendulum.
1st find the period
A pendulum has a length of 3.0 m and executes 20. complete
vibrations in 70. seconds.
1.
f = cycles / seconds
= 20 cycles / 70 seconds
= 0.286 hz
2.
T=1/f
= 1 / 0.286 seconds
= 3.5 seconds
Next find “g”
Find the acceleration of
gravity at the location of the
pendulum.
T= 3.5 seconds
Heads up!!
If you ÷ by 2 π 
Use (2 π ) !!
3.5 s = 2π√(3.0/g)
3.5 s = 6.28 √(3.0/g)
Square both sides
12.25 = 39.43 (3.0/g)
12.25 = 118.3/g
12.25(g) = 118.3
Divide by 12.25
g = 9.658 m/s/s
g = 9.7 m/s/s