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Sound is produced by a vibrating body - class-VIII

Description: sound is produced by a vibrating body
Number of Questions: 30
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Tags: physics wave motion sound waves world of sounds
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The back and forth motion of an object is called

  1. vibration

  2. rotation

  3. translation

  4. linear motion


Correct Option: A
Explanation:

When a body moves constantly from one position to the other and back to the initial position, then this motion of the body is called vibration.

Sound is produced by vibration. Define vibration.

  1. Vibration is a rapid to and fro motion of the object.

  2. Vibration is a circular motion of the object.

  3. Vibration is a translational motion of the object.

  4. None of the above


Correct Option: A
Explanation:

Vibration is a rapid to and fro motion of the object. 

Which of the following will produce sound through vibration.

  1. A plastic scale when bent over the edge of a bench

  2. Saying 'Ah' for few seconds

  3. Plucking a rubber string by fingers

  4. All of the above


Correct Option: D
Explanation:

All vibration produces sound. In some cases vibrations are visible to our naked eyes but Observe that sound is produced by vibration in some cases they can only be felt not seen. In all the above activities sound can be produced.

Sound waves are mechanical waves.

  1. True

  2. False


Correct Option: A
Explanation:

yes, sound waves are mechanical waves.

so the answer is A.

Vibrating bodies produce ........

  1. Sound

  2. Heat

  3. Light

  4. None of these


Correct Option: A
Explanation:

all vibrating bodies produce sound

so the answer is A.

Which of the following instrument is not a percussion instrument?

  1. Mri dangam

  2. Dholak

  3. Ghatam

  4. Tabla


Correct Option: C
Explanation:

Ghatam is not a percussion instrument, whereas it is a ghana vadya.

The waves that transfer vibrations and disturbance are

  1. Sound waves

  2. Light waves

  3. Infrared waves

  4. Ultrasonic waves


Correct Option: A
Explanation:

Sound is a form of energy produced and transmitted by vibrating matter. Sound travels in waves. When sound moves through matter (solid, liquid, or a gas), the molecules of the matter move backward and forward in the direction in which the wave is travelling. This movement is called a vibration. Sound travels more quickly through solids than through liquids and gases because the molecules of a solid are closer together. Sound travels the lowest through gases because the molecules of a gas are farthest apart. In a vacuum sound cannot travel because there is no matter for it to move through.
Hence, the sound waves transfer vibrations or disturbance to produce sound.

A to and fro motion by an object is also called 

  1. periodic motion

  2. oscillatory motion

  3. cyclic motion

  4. none of these


Correct Option: B
Explanation:

    Periodic motion is defined as the motion which is repeated identically after a fixed interval of time , to and fro motion is not necessary here .

    Oscillatory motion is that motion in which body moves to and fro about a fixed point in a fixed interval of time .
    In a cyclic motion , body returns at its initial position after a time .

Sound is produced in a bamboo flute because:

  1. air starts vibrating

  2. bamboo starts vibrating

  3. air hits the bamboo

  4. direction of air is changed


Correct Option: A
Explanation:

   When we put air in a bamboo flute by our mouth , we give energy to the air inside the flute and air inside the bamboo flute starts vibrating and we get a sweet sound .

The membrane of a drum vibrates to produce sound. Similarly the string of a sitarvibrates to produce sound. Based on these two examples answer the following question. Which part of a whistle vibrates to produce sound?

  1. body of whistle

  2. air

  3. mouth of the person

  4. all ofthe above


Correct Option: B
Explanation:

The vibrations produced in the air while blowing a whistle, produces sound.

In Dholak sound produce due to which of the following?

  1. Stretched membrane  

  2. Stretched strings

  3. Vibration of  air

  4. Air column 


Correct Option: A
Explanation:

When the sticks hit on the surface of the membrane, the membrane vibrates and results in the production of sounds.

So answer is A

What do you think a tabla player does to increase the pitch of the sound produced?

  1. He strikes the table skin harder.

  2. The pitch cannot be changed in a table.

  3. He tightens the skin by stretching the string around it.

  4. He gets a bigger tabla.


Correct Option: C
Explanation:

Answer is C.

The top of the tabla drum is covered with a stretched, layered leather membrane held in place by leather braces. The wooden pegs between the braces and the drum adjust the tension in the braces, thus controlling the pitch of the instrument.
Hence, to increase the pitch of the sound produced the player tightens the skin by stretching the string around it.

The part of the violin which vibrates while playing it is :

  1. the wire

  2. the box of the violin

  3. both the wire and the box

  4. none of the above


Correct Option: C

When a glass filled with water is struck with a stick, ripples are produced in the water. This indicates that

  1. the glass is not vibrating.

  2. the glass may or may not be vibrating.

  3. the glass is vibrating.

  4. none of the above is true.


Correct Option: C
Explanation:

When a glass filled with water is struck with a stick, it vibrates and this vibration creates ripples in the water. These ripples prove that the glass vibrates. Also, a sound is produced due to the vibration of the glass.

Which of the following musical instruments is a wind instruments?

  1. Flute

  2. Drums

  3. Piano

  4. All of these


Correct Option: A
Explanation:

Flute is played by blowing air into the instrument. So, it is a blow / wind instrument. Drums are played by hitting on its stretched membrane. So, it is a beat instrument.

Piano is played by hitting stretched strings inside with hammers. So, piano is a string instrument.

Why does a guitarist need to tighten the strings of the guitar to get the correct music and sound ?

  1. Tight strings force the entire guitar to vibrate.

  2. It is easy to play a guitar with tight strings.

  3. Tight strings look good and enhance the look of the guitar.

  4. It is not important to tighten the string.


Correct Option: A
Explanation:

When a guitarist plucks the strings of a guitar, the strings vibrate and force the entire guitar to vibrate as well. The sound that we hear is produced due to the vibration of the entire instrument. If the strings are not tight enough the entire instrument may not vibrate and the correct sound may not be obtained.

One of vibrations of strings makes

  1. pitch of the instrument

  2. pitch of the note

  3. scale of the note

  4. pitch of the scale


Correct Option: B
Explanation:

vibrations in the string makes or produces notes .

 notes are measured in terms of  pitch of the note.
so the answer is B.

If we tighten the stretched strings of guitar, then pitch will be 

  1. lower

  2. higher

  3. same

  4. dependent upon size of instrument


Correct Option: B
Explanation:

Pitch of sound depends on frequency. The frequency of sound emitted by a stretched string depends upon the tension on the string.  Greater tension means greater frequency, which means greater pitch. When we tighten the string of an instrument we are increasing the tension on the string. This increases the frequency. Hence pitch increases

Tuning fork causes them to vibrate and produce sound. This is due to 

  1. the two metal prongs of that tuning fork

  2. the length of the prongs of that tuning fork

  3. the speed of the molecules hit the tuning fork

  4. both A and B


Correct Option: A
Explanation:

tuning  fork has two metal prongs which are vibrated and sound is produced so the answer is A.

Which of the following vibrating parts of instrument is not matched with the respective instrument?

  1. Drum- Stretched Membrane

  2. Tabla - Stretched Membrane

  3. Mridangam - Stretched Membrane

  4. None of the above


Correct Option: D
Explanation:

all the instruments given here correctly matches with their vibrating parts.

so the answer is D.

Which of the following is the vibrating part of Saxophone?

  1. Stretched -Membrane

  2. Stretch-String

  3. Air column

  4. None of the above


Correct Option: C
Explanation:

Wind instruments are those which are played by blowing air into them through the human mouth.  They include saxophone,  trumpet, flute etc. In any wind instrument,  it is the air column which vibrates with a specific tone and produces music.

In violin there is part which  is used to adjust the string for getting right pitch. What is the name of that part?

  1. Tunning peg

  2. Volute

  3. Finger board

  4. Neck


Correct Option: A
Explanation:

tunning peg is used to adjust the string for getting right pitch in violin

so the answer is A.

Which of the following is/are  percussion instruments?

  1. Bell

  2. cymbals

  3. drum

  4. All of the above


Correct Option: D
Explanation:

Percussion instruments are those which are played by hitting on the membrane of that instrument. They include instruments such as tabla, bell drum, cymbals etc.

Which of the following is the vibrating part of Banjo?

  1. Stretched- Membrane

  2. Stretched- String

  3. Air column

  4. None of the above


Correct Option: B
Explanation:

String instruments are those which are played by manually vibrating the strings made of metal. When these strings are made to vibrate they emit a sound of a specific tone and produce music. Examples of such instruments are Banjo, guitar,  violin and so on. 

Assuming that the period of vibration of a tuning fork depends upon the length $l$ of its prongs density $\rho$ of its material and the elastic constant  $E$ of its material what would be the formula for the period of its vibration.

  1. $\frac{k}{l}\sqrt{\frac{y}{d}}$

  2. $\frac{2k}{l}\sqrt{\frac{y}{d}}$

  3. $\frac{k}{2l}\sqrt{\frac{2y}{d}}$

  4. $\frac{3k}{l}\sqrt{\frac{y}{2d}}$


Correct Option: A
Explanation:

Considering $n=k{l}^{a}{d}^{b}{y}^{c}$--------(A) 

where k=dimensionless quantity 
l=length $=L$;  d=density$=kg/{m}^{3}$ and y=Young modulus$=kg/m{s}^{2}$
Substituting the above mentioned dimension in A we get,
$[{T]}^{-1}=[{L]}^{a}[{M{L}^{-3}]}^{b}[{M{L}^{-1}{T}^{-2}]}^{c}$
Comparing the power of $ML$  and $T$ we have,
$b+c=0$---------(1)
$a-3b-c=0$------(2)
$-2c=-1$
$c=\dfrac{1}{2}$
Putting the values of c in 1 we get,
$b=\dfrac{-1}{2}$
 Putting the values of b and c in 2 we get,
$a=-1$
Thus putting the values of a,b and c in A we get,
$n=k{l}^{-1}{d}^{1/2}{y}^{1/2}=\dfrac{k}{l}\sqrt{\dfrac{y}{d}}$ 

Match the following and choose the correct answer.

A String vibration 1 Tabla
B Membrane vibration 2 Bicycle bell
C Vibration of air 3 Sitar
D Vibration of plate 4 Flute
  1. A-1, B-2, C-3, D-4

  2. A-2, B-1, C-4, D-3

  3. A-3, B-1, C-4, D-2

  4. A-4, B-3, C-2, D-1


Correct Option: C
Explanation:

String vibration is there in sitar.

Membrane vibration is there in tabla.
Vibration of air is in flute.
Vibration of plate is in bicycle bell.

The membrane of a drum vibrates to produce sound. Similarly the string of a sitar vibrates to produce sound. Based on these two examples answer the following question. Which part of a whistle vibrates to produce sound?

  1. Body of whistle

  2. Air

  3. Mouth of the person

  4. All of the above


Correct Option: A
Explanation:

A body of whistle is responsible for the whistle to produce sound.

As air enters the whistle at one end.As the air reaches the other, closed end, all the air molecules fill up on top of each other and cause a high pressure region.The air escapes out the little hole in the end making a sound you hear.The frequency of sound depends on the length of the whistle.

Percussion instruments are musical instruments that are played by

  1. banging

  2. shaking

  3. both A and B

  4. hitting


Correct Option: C
Explanation:

Percussion instruments are musical instruments that are played by banging and shaking both.

so the answer is C.

If we strike a water-filled bowl with spoon, then why there is variation in the sound produced due to change in water level of the bowl?

  1. due to change in pitch

  2. due to change in amplitude

  3. both A and B

  4. None of the above


Correct Option: A
Explanation:

Due to change in air column the wavelength and fundamental frequency changes. So the pitch of the sound changes which results in difference in the produced sounds .

so the answer is A.

Name the instruments for which more than one part is responsible for the production of sound.

  1. Tabla

  2. Violin

  3. Guitar

  4. All of the above


Correct Option: A
Explanation:

In violin and guitar, only the string is responsible for sound production. Whereas in Tabla, the diaphragm, as well as the air in the Tabla, produce sound.

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