Need: NotebookCLASS Notes:

Pendulum Lab with ClocksHandouts: Two reading (no notes)

Two HW sheets

Quiz Monday on pendulum problems

Start Pendulum clock lab on Monday alsoPlease Place Papers in the bin. If absent write dates on top

Retake Dates• See How They Run late -50%• Barbie and Ken Lab late -20% • Hooke’s Law Quiz Redo by Friday• Hooke’s Dry Lab Late -50% ONLY Rewrite if NY • Reaction time lab Late -50% • All other tests and quizzes ONLY Retake if NY• All other Labs Late -50% 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.

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

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.

• 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

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.

The frequency of swing is _________.

glenbrook.k12.il.us

Do not leave answer as a fraction

Frequency:Pendulums

Practice Problem on whiteboardUse 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 ________.

glenbrook.k12.il.us

Do not leave answer as a fraction

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 frequency?

•f = 8/60

•f=0.13 Hz or 0.13/sec or 0.13 sec-1

•What is the Period, T?

•T=1/f

•T=1/.13

•T=7.5 sec

What is the total time, t? 60sec

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

39.44L = 14.7 m

Now you try a problem.• The period of a simple pendulum is 2

seconds. Find its length.

= 1 meter

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.

Another problem

1st find the periodA 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.

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

T= 3.5 seconds

Heads up!!

If you ÷ by 2 π Use (2 π ) !!

g = 9.7 m/s/s