questions in short. [3 marks ]

Question 13 Marks

Arrange the following sounds in the order of increasing frequencies $($keeping the sound of lowest frequency first$):$
$a.$ Baby's voice.
$b.$ Man's voice.
$c.$ Woman's voice.

Answer

The following sounds in the order of increasing frequencies:
$a.$ Man's voice.
$b.$ Woman's voice.
$c.$ Baby's voice.

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Question 23 Marks

Three different vibrating objects produce three types of sounds $X, Y$ and $Z$. The sounds $X$ and $Y$ cannot be heard by a man having normal range of hearing but sound $Z$ can be heard easily. The sound $X$ can be heard by a bat whereas the sound $Y$ can be heard by a rhinoceros. What type of sounds are $X, Y$ and $Z?$

Answer

$X$: Ultrasonic sound waves (Greater than $20,000Hz). Y$: Infrasonic sound waves $(0-20 Hz). Z$: Audible sounds $(20Hz-20,000Hz).$

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Question 33 Marks

Name the part which vibrates to produce sound in the following:
$a.$ Drums.
$b.$ Sitar.
$c.$ Flute.

Answer

$a.$ Its stretched membrane.
$b.$ Its strings.
$c.$ Its long hollow pipe.

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Question 43 Marks

Your parents are going to buy a house. They have been offered one house on the roadside and another house three lanes away from the roadside. Which house would you suggest your parents should buy? Explain your answer.

Answer

There will be more noise in the house which is along the roadside due to noise produced by transportation vehicles. But, the house which is three lanes away from the roadside would have comparatively less noise . Therefore, it is better to take the house that is three lanes away from the roadside.

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Question 53 Marks

Which of the following is the speed of sound in water and which in steel?
$a. 5000\ m/s.$
$b. 1500\ m/s.$
$c. 340\ m/s.$

Answer

The speed of sound is faster in solid as compared to liquid, and then slowest in gases. Thus, the speed of sound is more in steel, then water and then air.
$a. 5000\ m/s -$ Speed of sound in steel.
$b. 1500\ m/s -$ Speed of sound in water.
$c. 340\ m/s -$ Speed of sound in air.

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Question 63 Marks

How do astronauts talk to one another on the surface of moon and why?

Answer

The astronauts have sound transmitting devices in the helmets they wear which help them exchange sound waves with one-another. This is because moon does not have any atmosphere and sound its does not have any medium for sound to travel as sound does not travel in vacuum.

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Question 73 Marks

What is the name of passage in outer ear which carries sound waves to the eardrum?

Answer

As seen from the figure given below, the sound is carried through the Ear canal.

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Question 83 Marks

Name one solid, one liquid and one gas through which sound can travel.

Answer

Solid: Metal $-$Iron, Aluminium etc.
Liquid: Water.
Gas: Air.

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Question 93 Marks

The sound from an insect is produced when it vibrates its wings at an average rate of $500$ vibrations per second:
$a.$ What is the time$-$period of the vibrations?
$b.$ What is the frequency of the vibrations in hertz?
$c.$ Can we hear this sound? Why or why not?

Answer

$a.$ The time period $= \frac{1}{\text{f}}= \frac{1}{500}=0.002$ secs.
$b.$ The frequency of the vibrations in hertz is $500Hz.$ Because $1Hz = 1$ vibration/ second.
$c.$ We can hear this because it is in the range of $20H_z$ to $20,000H_z$.

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Question 103 Marks

Give two causes of noise pollution from the homes.

Answer

The causes of noise pollution are as follows:
$a.$ Televisions running at high volumes.
$b.$ Use of Loudspeakers in religious or other functions.
$c.$ Use of crackers.

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Question 113 Marks

A pendulum oscillates $40$ times in $4$ seconds. Calculate its.
$a.$ time$-$period, and
$b.$ frequency.
Can we hear the sound produced by the oscillations of this pendulum? Give reason for your answer.

Answer

Frequency $=\frac{\text{40 vibration}}{\text{4 seconds}}=10\text{Hz}$ Thus, time period $=\frac{1}{\text{f}}=\frac{1}{10}=0.1$ seconds. No, we cannot hear because the audible human range is from $20Hz$ to $20,000Hz.$

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Question 123 Marks

Explain why, the flash of lightning is seen first but the sound of thunder is heard a little later (though lightning and thunder take place in the sky at the same time and same distance from us).

Answer

The flash of lightning is seen first but the sound of thunder is heard a little later though lightning and thunder take place in the sky at the same time and same distance from us, because, the velocity of light in air is $3\times 108 m/s$ while the velocity of sound in air is $343 m/s$. Thus, we can see light first and thunder sound later.

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Question 133 Marks

Name the three tiny bones present in the middle part of ear.

Answer

The three tiny bones – the malleus, incus, and stapes – are found in the middle ear. Each bone is named in Latin for its shape.

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Question 143 Marks

Name any two common musical instruments and identify their vibrating parts.

Answer

Dholak.	Diaphragm (stretched membrane).
Sitar.	Strings of the Sitar.
Flute.	Air column inside the flute.

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Science questions in short. [3 marks ]

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