5.2 Damping and Resonance

MODUL PDP SPM PASCA PKP
NEGERI PERAK 2020

PHYSICS Form 4

5.2: Damping and Resonance

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5.2 Damping and Resonance

Learning Standard:

Pupils are able to:

• describe damping and resonance for an oscillating/ vibrating system.
• justify the effects of resonance in our daily lives.

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5.2 Damping and Resonance

Damping and Resonance for an Oscillating and Vibrating System
1. An oscillating system that is displaced and then left to oscillate without the action of

external forces, will oscillate at a certain frequency that is called natural frequency.
2. In fact, an vibrating system will finally stop or its amplitude decreases with time.
3. This is due to damping process.
4. DAMPING process is a process that LOSSES ENERGRY in the vibrating system in the form

of heat.

Amplitude

Unchanged frequency

DAMPING OF OSCILLATION

Energy decerases Amplitude decreases Period / Frequency unchanged

Only ENERGY and AMPLITUDE that decerases, but PERIOD of oscillation and FREQUENCY
unchanged.

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FACTORS OF DAMPING

EXTERNAL DAMPING INTERNAL DAMPING

Oscillating system loses energy to Oscillating system loses energy
overcome friction or air because of the stretching and
resistance. compression of the vibrating

particles in the system.

5. Resonance means a system that oscillates with the maximum amplitude.
6. Resonance occurs when a system oscillates with the same frequency with its natural

frequency.
7. The system oscillates with the maximum amplitude because it receives maximum energy

from the system that forces it to oscillate.

Frequency of external force = Natural frequency

RESONANCE Maximum energy
transferred

Experiment to show resonance System oscillated
with maximum

amplitude

Oscillate bob X.
Found that all bobs oscillate.
But bob D oscillates with maximum amplitude.
It is because the length of bob X = length of bob D.
Frequency of oscillation of bob X = Frequency of
oscillation of bob D.
Bob D oscillates with maximum amplitude produces
the phenomenon of resonance.

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APPLICATIONS OF RESONANCE :

1. The soldiers in a march cannot stomp their feet
simultaneously when crossing a bridge. This is to prevent
the bridge from vibrating at its natural frequency that
might damage the bridge.

2. Musical instruments such as trumpet, and saxophone
produce sound because of resonance effect.

3. Tuning fork can be used to tune the frequency of a piano
string or guitar string because of resonance effect.

4. Resonance effect can be used to the radio frequency and
television to receive signal from different networks.

EXAMPLES OF RESONANCE PHENOMENA:
Phenomenon 1:
Soprano singer sings at the same frequency as the natural
frequency of the vibration of glass. Maximum vibration of the
glass causes the glass to break.
Phenomenon 2:
Strong wind causes the bridge to vibrate at the same frequency
as its natural frequency. The bridge will collapse due to the
vibration of the bridge at maximum amplitude.

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5.2 MIND MAP

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5.2 FAQ

No Questions and Answers
1 Q What is damping of a wave?

A A damped wave is a wave whose amplitude of oscillation decreases with
time, eventually going to zero.

2 Q What are the causes of damping?

A Damping is caused by such energy losses as occur in liquid lubrication
between moving parts or in a fluid forced through a small opening by a piston,

as in automobile shock absorbers.

3 Q Does damping change the natural frequency?

A The amplitude of the resonance peak decreases and the peak occurs at a
lower frequency. So damping lowers the natural frequency of an object and
also decreases the magnitude of the amplitude of the wave.

4 Q What is resonance?

A Resonance describes the phenomenon of increased amplitude that occurs
when the frequency of a periodically applied force is equal or close to a
natural frequency of the system on which it acts.

5 Q What is the importance of resonance in music?

A In music, resonance is used to increase the intensity (loudness) of a sound.
The comparatively weak vibrations produced at the end of an organ pipe, for
example, cause a column of air in the pipe to vibrate in resonance, thus
greatly increasing the loud-ness of the sound.

6 Q Where can resonance occur?

A Resonance only occurs when the first object is vibrating at the natural
frequency of the second object.

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5.2 Exercise

SECTION A

1 Diagram below shows two identical tuning forks side by side in a laboratory. When a
student knocks on the first fork, the vibrations of the first fork have forced the
second fork to oscillate with its maximum amplitude.

Which phenomenon will best describe the situation? [MEMAHAMI]

A Damping
B Resonance
C Modulation
D Echo

2 The Diagram below shows a pendulum which is displaced to swing with a period of
2s. It is allowed to swing until it stops

Which of the following graphs show the oscillation of the pendulum? [MEMAHAMI]
A Displacement

Sesaran

2 4 6 Time /s
Masa /s

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B Displacement 4 6 Time /s
Masa /s
Sesaran
2 4 6 Time /s
Masa /s
C Displacement
4 6 Time /s
Sesaran Masa /s

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D Displacement

Sesaran

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3 A system is oscillated at a frequency equivalent to its natural frequency by an
external force.
This phenomenon is called
[MENGETAHUI]

A Damping
B Resonance
C Rectification
D Pitching

4 Observe the situation below

The vibration of a bus becomes very noisy when the bus is
moving at a certain speed. This is because at certain
speeds some parts of the bus are forced to vibrate at their
original frequency with maximum amplitude

The phenomena is known as [MEMAHAMI]

A Loudness
B External damping
C Resonance
D Internal damping

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5 System A is forced to vibrate by system B. Resonance is said to occur when system A

[MEMAHAMI]

A oscillates with maximum velocity.

B vibrates with maximum amplitude.

C vibrates with maximum frequency.

D oscillates with maximum wavelength.
.

SECTION B
1 Diagram shows a Barton Pendulum.

When the X pendulum swings, the pendulum A, B and C also will swing.

(a) What is frequency?

[MENGETAHUI]

……………………………………………………………………….…………………………………………

[1 mark]

(b) Based on the above diagram

(i) Explain why the pendulum W A, B and C also will swing

[MEMAHAMI]

……………………………………………………………………….…………………………………………

[1 mark]

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(ii) Which pendulum will swing at maximum amplitude

[MEMAHAMI]

……………………………………………………………………….…………………………………………

[1 mark]
(c) State a physical phenomenon that could explain the above situation

[MENGETAHUI]

……………………………………………………………………….…………………………………………
[1 mark]

2 Diagram 2.1 shows an oscillating pendulum in water. The oscillating pendulum
experiences damping.
Diagram 2.2 shows the displacement-time graph for the oscillating pendulum.

Diagram 2.1
Rajah 2.1

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(a) State the quantity which decreases gradually and becomes zero in damping.
[MENGETAHUI]

……………………………………………………………………….…………………………………………
[1 mark]

(b) State one reason for the occurrence of damping in this system
[MEMAHAMI]

……………………………………………………………………….…………………………………………
[1 mark]

(c) Based on Diagram 2.2, find
[MEMAHAMI]

(i) the period of the oscillating system.
……………………………………………………………………….…………………………………………

[1 mark]
(ii) the frequency of the oscillating system.
……………………………………………………………………….…………………………………………

[1 mark]
(d) What happens to the period of the oscillating system when a longer pendulum

is used?
[MEMAHAMI]

……………………………………………………………………….…………………………………………
[1 mark]

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Title 5.2 QR CODE QR CODE

Damping and 5.2 Damping and Resonance
Resonance
link
https://youtu.be/bkpFpRQACJ8

Damping & https://youtu.be/Nm8Uto6Do90
Resonance

How to see damped https://youtu.be/avOhWrv2qQ8
oscillations

Resonance Pendulum https://youtu.be/qa8_AoqzdMU

REINFORCEMENT https://drive.google.com/file/d/1t3h6YElNfTL26tsfeHJPlu
TEST pXkxaF5a7y/view?usp=sharing

ANSWER https://drive.google.com/file/d/1bL670F7wMZVw62cC8R
REINFORCEMENT Ef8Fy3TgFmt-3x/view?usp=sharing
TEST

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5.2 Answer

Answer

Section A

1. B
2. A
3. B
4. C
5. B

Section B Number of complete oscillation in one second
1 (a) (i) Energy is transfered
(ii) Pendulum B
(b) resonance

(c)

2 (a) Amplitude

(b) Energy is used to overcome frictional force

(c) (i) 2 s
(ii) 0.5 Hz

(d) The period increase

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