Download - Tyas - Vibration & Wave 2011 (2003 verse)
-
8/7/2019 Tyas - Vibration & Wave 2011 (2003 verse)
1/31
Tyas Ajeng Puspitasari, S.Pd
Grade VIII Semester 2
2010/2011
Junior High School 1 Malang
www. tyas-physics.blogspot.com
-
8/7/2019 Tyas - Vibration & Wave 2011 (2003 verse)
2/31
CONTENT
Basic Competency & Indicator
VIBRATION
Displacement and Amplitude
Period and Frequency
Experiment to investigate period of pendulum swing Resonance
Problems of Vibration
WAVE
Kinds of Wave
Transversal and Longitudinal Wave
Calculate Speed of wave
Problems of wave
2
HOME
www. tyaswww. tyas--physics.blogspot.comphysics.blogspot.com
-
8/7/2019 Tyas - Vibration & Wave 2011 (2003 verse)
3/31
www. tyaswww. tyas--physics.blogspot.comphysics.blogspot.com
Basic Competency Students can plan and do the analysis of data in
the experiment of vibration and waves
1. To identify the movement of vibration with an experiment.
2. To determine the amplitude, period, and frequency of a vibration.
3. To measure period and frequency of vibration
4. Compare the characteristics of transversal and longitudinal waves
5. Investigate the wavelenght on the rope/slinky for transversal and longitudinal
wave.
6. To describe the relation of speed of traveling wave, frequency and wavelength
Objectives:
3
HOME
-
8/7/2019 Tyas - Vibration & Wave 2011 (2003 verse)
4/31
www. tyas-physics.blogspot.com
-
8/7/2019 Tyas - Vibration & Wave 2011 (2003 verse)
5/31
Have you ever played a swing?
5
HOME
www. tyaswww. tyas--physics.blogspot.comphysics.blogspot.com
-
8/7/2019 Tyas - Vibration & Wave 2011 (2003 verse)
6/31
Vibration is an oscillatingmovement through apoint of equilibrium
Vibration also known as Simple Harmonic Motion (SHM)
The restoring force also
leads to SHM when theobject is attached to a
vertical spring
6
HOME
www. tyaswww. tyas--physics.blogspot.comphysics.blogspot.com
What is a vibration ?
-
8/7/2019 Tyas - Vibration & Wave 2011 (2003 verse)
7/31
Now, pay attention to theseat of the swing a boy is
sitting on in figure beside.
When it is not yet moved,
its position is at point O
This point is the
equilibrium
Point of Equilibrium
7
HOME
www. tyaswww. tyas--physics.blogspot.comphysics.blogspot.com
-
8/7/2019 Tyas - Vibration & Wave 2011 (2003 verse)
8/31
Displacement, is any distance between
the vibrating thing and its equilibrium
point.
The maximum displacement of a
vibration is called Amplitude (A)
Displacement and Amplitude
Amplitude (A)
The amplitude of a vibration is
related to the energy of the
vibration. If its amplitude is big, so
its energy is big too.
8
HOME
www. tyaswww. tyas--physics.blogspot.comphysics.blogspot.com
-
8/7/2019 Tyas - Vibration & Wave 2011 (2003 verse)
9/31
One Vibration
B O A
1 vibration =
movement from
A-O-B-O-A.
9
HOME
www. tyaswww. tyas--physics.blogspot.comphysics.blogspot.com
-
8/7/2019 Tyas - Vibration & Wave 2011 (2003 verse)
10/31
B
O
C
O is point of Equilibrium
1 Vibration: C-O-B-O-C
B-O-C-O-B
Vibration: C-O-B
B-O-C
Vibration: C OB O
A is Amplitude
1
HOME
www. tyaswww. tyas--physics.blogspot.comphysics.blogspot.com
Vibration of pendulum swing
-
8/7/2019 Tyas - Vibration & Wave 2011 (2003 verse)
11/31
Period (T) is the time needed to do one vibration
11
HOME
www. tyaswww. tyas--physics.blogspot.comphysics.blogspot.com
Period
n
t
T!
t = time needed (s)
n = number of vibration
The unit of period is second
For example, the time needed for a vibration is 0.5 seconds, so T = 0.5 seconds.
-
8/7/2019 Tyas - Vibration & Wave 2011 (2003 verse)
12/31
Frequency (f) the number of vibrations which happens
every second.
12
HOME
www. tyaswww. tyas--physics.blogspot.comphysics.blogspot.com
Frequency
t
n
f!
t = time needed (s)
n = number of vibration
The unit of frequency is 1/second or Hertz (Hz)
If the frequency of vibration is 50Hz it means there is any 50 times oscillations
in every second
-
8/7/2019 Tyas - Vibration & Wave 2011 (2003 verse)
13/31
Period is inversely proportional withfrequency
The Relation of Period and frequency
13
HOME
www. tyaswww. tyas--physics.blogspot.comphysics.blogspot.com
fT
1!
Example:
Calculate the frequency of the vibration of a ruler if its period is 0.02
seconds.
Tf
1
!
Given: T= 0.02 sQuestion:f
Answer: Hzss
f 502
00
02.0!!!!
-
8/7/2019 Tyas - Vibration & Wave 2011 (2003 verse)
14/31
1. In 5 seconds, there are 200 times vibration
a. What is the frequency of this vibration?
b. What is the period of this vibration?
2. If the frequency of a vibration is 400 Hz
a. What is the period?
b. How many times the object vibrate for 60 seconds?
3. A pendulum can oscillate 100 times in 10 minutes.
What is the period of the oscillation?
14
HOME
www. tyaswww. tyas--physics.blogspot.comphysics.blogspot.com
Problems of Vibration #1
-
8/7/2019 Tyas - Vibration & Wave 2011 (2003 verse)
15/31
1. An object vibrates for 40 times in second. The frequency and
the period of the vibration is
2. An object vibrates 50 times in 25 seconds between two points
with a distance of 30 cm
a. What is the frequency of vibration?
b. What is the period of vibration?
c. The amplitude of the vibration is cm
3. If the time needed to move from A to B is 0.05 second
then the number of vibrations in 2 seconds are
4. A pendulum is released from its maximum displacement, after
60 seconds, the pendulum has completed 20 cycles. Calculate
the period and frequency.
15
HOME
www. tyaswww. tyas--physics.blogspot.comphysics.blogspot.com
Problems of Vibration #2
B OA
-
8/7/2019 Tyas - Vibration & Wave 2011 (2003 verse)
16/31
EXPERIMENT TO INVESTIGATE THE PERIOD OFPENDULUM SWING
OBJECTIVES
To investigate factors that influence period of a pendulum swing.PROBLEM
Is the period of a pendulum influenced by its amplitude?
Is the period of a pendulum influenced by its thread length?
Is the period of a pendulum influenced by its mass?
HYPOTHESIS
*Make hypothesis to estimate the period of a swing if its amplitudeincreases?
MATERIALANDAPPARATUS
a swinging pendulum
a ruler
threada stopwatch or watch
a static upright rod and its clamp
PROCEDURE
*Arrange the steps you will use to examine your hypothesis
16
HOME
www. tyaswww. tyas--physics.blogspot.comphysics.blogspot.com
-
8/7/2019 Tyas - Vibration & Wave 2011 (2003 verse)
17/31
Periodof s ing pendulum is not influenced
y amplitude andpendulums mass
CONCLUSIONFROM THE EXPERIMENT
Periodof s ing is influenced y t readlengt
T e longer t read lengt , t e longer t e
periodof pendulum
17
HOME
www. tyaswww. tyas--physics.blogspot.comphysics.blogspot.com
-
8/7/2019 Tyas - Vibration & Wave 2011 (2003 verse)
18/31
when one object vibrating at the same naturalfrequency of a second object forces that secondobject into vibration motion.
The effect of resonance is in the form of an
increase in the amplitude of its vibration. Without resonance we wouldn't have radio,
television, music, or swings on playgrounds.
Of course, resonance also has its dark side. It
occasionally causes a bridge to collapse, ahelicopter to fly apart, or other inconveniences.
RESONANCE
18
HOME
www. tyaswww. tyas--physics.blogspot.comphysics.blogspot.com
-
8/7/2019 Tyas - Vibration & Wave 2011 (2003 verse)
19/31
Resonance is not always advantageous. In 1831, a suspension bridge in England fell
down because it had resonance with the
trotting shoes of an army marching on it.
In 1940, the Tahoma bridge in USA fell down
because it had resonance with the effect of a
blast of strong wind.
RESONANCE
19
HOME
www. tyaswww. tyas--physics.blogspot.comphysics.blogspot.com
-
8/7/2019 Tyas - Vibration & Wave 2011 (2003 verse)
20/31
When object x swings ,
which pendulum do
you think will swings
too?
RESONANCE
Why????
P
endulumC
!!
The pendulums swing with the same
frequency
Frequency of pendulum is depend on theirthread length and gravitational acceleration
So, pendulum with the same thread length
with the swinging object will swings too
-
8/7/2019 Tyas - Vibration & Wave 2011 (2003 verse)
21/31
www. tyas-physics.blogspot.com
-
8/7/2019 Tyas - Vibration & Wave 2011 (2003 verse)
22/31
22
HOME
www. tyaswww. tyas--physics.blogspot.comphysics.blogspot.com
Wave
Awave is a disturbance travelling withdefinite energy from one place to another
You can make a wave on a rope.
In this case, the rope is called amedium
-
8/7/2019 Tyas - Vibration & Wave 2011 (2003 verse)
23/31
23
HOME
www. tyaswww. tyas--physics.blogspot.comphysics.blogspot.com
When the disturbance moves through the medium,
the particles of the medium only move up and
down (or closer and farther apart).
Do the particles of the medium follow the movement of
the wave?
While moving, the wave does not
carry particles of the medium
A wave carries ENERGY from one
place to another.
so, what is carried
by a wave?
-
8/7/2019 Tyas - Vibration & Wave 2011 (2003 verse)
24/31
Wave
Mechanic Wave
RequireMedium
Example:
Ocean waves, seismic waves,sound waves
Electromagnetic Wave
needs no mediumto travelling
Example:Light, Radio waves, X-rays
24
HOME
www. tyaswww. tyas--physics.blogspot.comphysics.blogspot.com
-
8/7/2019 Tyas - Vibration & Wave 2011 (2003 verse)
25/31
Rarefaction
25
HOME
www. tyaswww. tyas--physics.blogspot.comphysics.blogspot.com
Kindof ave
Transverse Wave
The direction of its vibration is perpendicular to the
movement direction of wave
Longitudinal Wave
The direction of its vibration is parallel to the movementdirection of wave
-
8/7/2019 Tyas - Vibration & Wave 2011 (2003 verse)
26/31
26
HOME
www. tyaswww. tyas--physics.blogspot.comphysics.blogspot.com
Transverse Wave
The movement directionof wave is perpendicular
to the direction of its
vibration
Example: Light, Water
wave, Ropes wave
A wavelength () is the distance between one point in a wave
and the nearest similar point in the wave.
Example: the distance from a crest to the nearest crest or from
a trough to trough
Large amplitude Large energy carried by wave
Small amplitude Small energy carried by wave
crest
-
8/7/2019 Tyas - Vibration & Wave 2011 (2003 verse)
27/31
27
HOME
www. tyaswww. tyas--physics.blogspot.comphysics.blogspot.com
Longitudinal Wave
The movement directionof wave is parallel to the
direction of its vibration
Example: Sound
A wavelength () is the distance between the two nearest
rarefactions or two nearest compressions.
-
8/7/2019 Tyas - Vibration & Wave 2011 (2003 verse)
28/31
28
HOME
www. tyaswww. tyas--physics.blogspot.comphysics.blogspot.com
Speed of wave
Remember
t
sv ! If the wave passes one wavelength (), itspassing time is the period of the wave (T),
and the previous formula can be rewritten as
Tv P
Relation offand T is:
Tf
1!
fv .P
v= speed of wave (m/s) = wavelength (m)
T= period (s)
f= frequency (Hz)
-
8/7/2019 Tyas - Vibration & Wave 2011 (2003 verse)
29/31
29
HOME
www. tyaswww. tyas--physics.blogspot.comphysics.blogspot.com
EXERCISE OF WAVE #1
1. From the figure of wave beside, find itsa. Amplitude
b. wavelength
c. Period 15 m
26
t (seconds)30
cm
2. Calculate the speed of the following wave
3. Calculate the speed of the following wave2seconds
3 m
-
8/7/2019 Tyas - Vibration & Wave 2011 (2003 verse)
30/31
2. To find speed , there are two ways:
Or find its wavelength and period first.
Then find the speed with formula:
Two variations way give the same result, that speed is equal to 4 m/s
1.
a. Amplitude = 15 cm
b. Wavelength :
c. Period
ANSWER
mmwaveofnumberropeoflength 10
5.1
15 !!!P
ss
waveofnumber
timetotalT 4
5
6!!!
sm
timetotal
lengthtotal4
6
24!!!P
m842 !v!Ps
sT 2
3
6!!
sTv 4
2
8!!!
P
3. From the picture, we already know the T = 2 seconds (distance between crestto crest)
Then find its wavelength
Thus its speed:
m
m
wa
o
numbr
ropo
ng
h2
5
3!!!P
sTv 1!!!
P
30
HOME
www. tyaswww. tyas--physics.blogspot.comphysics.blogspot.com
-
8/7/2019 Tyas - Vibration & Wave 2011 (2003 verse)
31/31