TS 8th Class Physical Science Study Material 5th Lesson Metals and Non-Metals

TS Board Telangana SCERT Class 8 Physics Solutions 5th Lesson Metals and Non-Metals Textbook Questions and Answers.

TS 8th Class Physics 5th Lesson Questions and Answers – Metals and Non-Metals

Reflections on concepts

Question 1.
How can you explain that sound has energy.
Answer:

  1. Take a cell phone in a plastic bottle.
  2. Cover the plastic bottle with stretched rubber balloon.
  3. Keep some sugar granules or sand on the balloon.
  4. When the cell phone in side is not playing songs the sand parficles on the diaphragm remains stationary.
  5. When the cell phone plays songs we can observe the vibration of the diaphragm where sand particles dancing is also observed.
  6. So we can conclude the sound produced inside the bottle is responsible for these vibrations. Thus sound has energy.

TS 8th Class Physical Science Study Material 5th Lesson Metals and Non-Metals 1

Question 2.
Write the unit to measure the sound intensity.
Answer:
The intensity of sound is measured in dB (decibles).

Question 3.
Write the differences between the noise and music?
Answer:

Noise Music
1) The sounds which are not pleasant to hear are called noise.
Eg: Dragging the almirah, machine, horn vehicles.
1) The sounds which are pleasant to hear are called music.
Eg: Playing veena, playing sitar etc.
2) Noise is the irregular combination of sounds. 2) Music is the combination of sounds that are produced in an order.
3) Noise has no characteristics of sound. 3) Musical note has three important characteristics of sound.

Question 4.
Explain the sources which produce sound pollution in your surroundings.
Answer:
Sources of sound causing sound pollution:

  1. Sounds of traffic and their horns.
  2. Sounds in constructions of buildings at sites.
  3. Sounds produced in industries.
  4. Sounds in mines.
  5. Sounds during explosions and bursting of crackers.
  6. Sound pollution in our homes like mixer/grinders washing machines and electric motors.
  7. Sounds due to printing machine.
  8. Sounds due to soldering and welding, tinkering.
  9. Sounds during the elections campaign.
  10. Sounds due to mikes during festivals.

Question 5.
Write your suggestions about reducing sound pollution.
Answer:
We cannot stop sound pollution but we can reduce sound pollution with some measures.
Steps to be taken to reduce sound pollution.

  1. Attach silencers to the bikes and other machines to reduce sounds.
  2. Manufacture machines that work with lesser noise.
  3. Use the TVs and tape recorders with low volumes in our home.
  4. Plant trees to reduce sound pollution.
  5. Avoid unnecessary usage of horns of vehicles.

TS 8th Class Physical Science Study Material 5th Lesson Metals and Non-Metals

Application of concepts

Question 1.
The sounds of crickets (insects) make us close our ears. Why?
Answer:
The sounds of crickets make us to close our ears because the frequency of their sound is high.
The frequency of the sounds of crickets is in ultrasonic range that is nearly 20,000 Hz. So we are unable to hear that sounds. So the sounds of crickets make us to close our ears.

Question 2.
Write the names of any three musical instruments that you know and explain how they produce sound.
Answer:

  • Veena, Tabala, and Flute are the three musical instruments known to me.
  • Veena produces sound by vibrating the stretched string.
  • Tabala produces sound by vibrating the stretched membrane.
  • A flute produces sound by vibrating the air column.

Question 3.
Draw the figures depicting low amplitude and high amplitude.
Answer:
TS 8th Class Physical Science Study Material 5th Lesson Metals and Non-Metals 2

Question 4.
“Vibrations in a body produce sounds”. How do you prove it?
Answer:
i. Put a hack-saw blade in between a table and a brick as shown in the figure and press it
and then leave abruptly. You listen to the sound and it is in vibrating mode.
TS 8th Class Physical Science Study Material 5th Lesson Metals and Non-Metals 3

ii. Ring your school bell and listen the sound carefully. Now hold the bell tightly with
your hands. You feel the vibration of bell when it is ringing. From the above experiments, you may notice that objects vibrate while they are producing the sound. Thus we can conclude that a vibrating body produces sound.

Question 5.
Write any two slogans to reduce sound pollution.
What we have learnt?
Answer:
“Avoid Sound Pollution – Save Bio-diversity”.
“Low Sound – Peaceful Mind’

Sound pollution affects the Bio-diversity. Vibrations of high frequency from cell phone tower cause the disappearing of sparrows. Crows and Eagles are also affected by the high frequency sound pollution. Hence Bio-diversity in nature collapsed.

TS 8th Class Physical Science Study Material 5th Lesson Metals and Non-Metals

Higher Order Thinking Questions

Question 1.
What is the effect of humidity on quality of sound propagation? is there any difference in propagation of sound in air during the summer and winter seasons? Discuss.
Answer:
Effect of humidity on quality of sound:

  1. Quality or timber is the characteristics of a sound wave which enables us to know the person who is speaking without seeing him.
    Eg: If you hear news in Radio, we can recognise whether it is of male or female.
  2. As the humidity in the atmosphere increases the quality of sound does not change.
  3. If the humidity increases speed of the sound increases.
  4. So in winter or on a cloudy day the speed of the sound increases and reaches the listener fastly.
  5. Even in summer also the speed of the sound increases. But it does not increase so much like in winter, since (v ∝\( \sqrt{\mathrm{T}}\)) Velocity of sound increases with square root of absolute temperature.

Question 2.
How does sound pollution effect Biodiversity? Explain.
Answer:
Sound pollution (or environmental sound) is displeasing human, animal or machine-created sound that disrupts the activity or balance of human or human life.

Sound can have a detrimental effect on animals by causing stress, increasing risk of death by changing the delicate balance in predator/prey detection and avoidance, and by interfering with their use of sounds in communication especially in relation to reproduction and in navigation. Acoustic overexposure can lead to temporary or permanent loss of hearing.

An impact of noise on animal life is the reduction of usable habitat that noisy areas may cause, which in the case of endangered species may be part of the path to extinction. Sound pollution has caused the death of certain species of whales that beached themselves after being exposed to the loud sound of military sonar.

Multiple Choice Questions

Question 1.
An object which moves to and fro motion from rest known as ……………… .[ ]
a) Linear motion
b) vibration
c) simple motion
d) Angular motion
Answer:
b) vibration

Question 2.
The number of vibrations produced per second is known as ………………… .[ ]
a) Frequency
b) Shrillness
c) Vibration limit
d) Decibels
Answer:
a) Frequency

Question 3.
The audible sound range of man is …………………. . [ ]
a) 10-10000 Vibrations/sec
b) 20-20000 Vibrations/sec
c) 30-30000 Vibrations/sec
d) 40-40000 Vibrations/sec
Answer:
b) 20-20000 Vibrations/sec

Question 4.
The oval window has the surface area ……………… of the eardrum. [ ]
a) 1/10
b) 1/20
c) 1/30
d) 1/40
Answer:
b) 1/20

TS 8th Class Physical Science Study Material 5th Lesson Metals and Non-Metals

Question 5.
The shrillness of a sound is known as ……………….. . [ ]
a) Pitch
b) Vibration
c) Intensity
d) decibel
Answer:
a) Pitch

Suggested Experiments

Question 1.
Conduct an experiment to know the relationship between the intensity of sound produced by a body and its amplitude.
Answer:

Aim: To know the relation between the intensity of sound produced by a body and the vibrators of the body.
Apparatus: Wooden table, hack-saw blade or metal scale of 30 cm long, and a brick.

Procedure:

  • Place the blade metal scale on the table with 10cm of the blade on the surface and rest of it in air.
  • Keep a heavy brick on one end of the blade which is kept on the table.
  • Vibrate the blade gently and observe the vibrations and simultaneously listen to the sounds.
  • Repeat the same, 2 – 3 times and record the observations in the table.
  • Now vibrate the blade using higher force. Observe the vibrations and listen to the sounds.
  • Repeat this for 2-3 times and record the observations.
Force Vibration of the blade scale Intensity of sound
Small force
Large force

From the above activity, we conclude that as the force, increases the displacement as well as amplitude increases.
TS 8th Class Physical Science Study Material 5th Lesson Metals and Non-Metals 13

So when amplitude of sound increases, intensity of sound also increases.

Questions based on the above Lab Activity – 1

a. When do you hear a loud sound?
Answer:
When the scale is vibrating we can hear loud sound.

b. When do you hear a feebler sound?
Answer:
When the blade is vibrating we can hear feebler sound.

c. What difference do you notice in number of vibrations of blade/scale during loud and feeble sounds?
Answer:
Blade gives more vibrations while scale gives less vibrations in one second.

Question 2.
Conduct an experiment to identify Pitch or Shrillness of different sounds.
Answer:

Aim: Identifying pitch or shrillness of a sound. (or) Identify the relation between pitch and frequency.
Materials required: Wooden table, two hack-saw blades or metal scales of 30cm length and a brick.

Procedure:

  • Place the first blade on the table with 10cm portion of the blade on the table and rest of it in air.
  • Keep brick as weight on the 10cm portion of the blade which was kept on the table.
  • Place the second blade on the table, with 25cm on the table and 5cm in air, Keep brick as weight on the scale. See the gap between two blades be 10 cm.

TS 8th Class Physical Science Study Material 5th Lesson Metals and Non-Metals 14

  • Vibrate both the blades with same force. Observe the vibrations and listen to the sound produced.
  • Repeat the same 2-3 limes and record observations in the table.
Blade length in air Vibrations Sound
Blade-1:25cm
Blade -2: 10cm

You mas notice that the number of vibrations produced by 25cm long blade is less than the number of vibrations produced by 10cm long blade.
The Sound produced by 10cm blade is more shrill than that of 25cm blade.
The shrillness of a sound is known as pitch.
The number of vibrations per second is called frequency.
The pitch of the sound depends upon its frequency.
In the above experiment more is the shrill, more is the pitch and it has more frequency.
Thus the sound produced a short blade (10cm) has high pitch and sound produced by (25cm) long blade has low pitch.

Questions based on the above Lab Activity

a. What difference do you notice in number of vibrations of two blades?
Answer:
We may notice that the number of vibrations produced are less in 25 cm long blade when compared to the vibrations of 10 cm long blade.

b. What difference do you notice in the quality of sound produced by them?
Answer:
The sound produced by 10 cm blade is more shrill when compared to that of 25 cm blade.

TS 8th Class Physical Science Study Material 5th Lesson Metals and Non-Metals

Suggested project works

Question 1.
Collect photographs showing various situations of sound pollution and prepare a report.
Answer:

  1. Function where loudspeakers are used
  2. Traffic ¡am and blowing horns
  3. Sound pollution because of firecrackers

TS 8th Class Physical Science Study Material 5th Lesson Metals and Non-Metals 4

Question 2.
Collect the photographs of different musical instruments and paste in your scrapbook.
Answer:
TS 8th Class Physical Science Study Material 5th Lesson Metals and Non-Metals 5

Question 3.
Collect the photographs of local musicians and exhibit them in your class.
Answer:
TS 8th Class Physical Science Study Material 5th Lesson Metals and Non-Metals 6

Do you know?

Golconda Fort – Hyderabad
It is a famous fort in India. It is famous for many engineering and architectural marvels. If you clap your hands at a particular point under the dome it reverberates and can be heard at the highest point of the fort which is about 1 km away.
TS 8th Class Physical Science Study Material 5th Lesson Metals and Non-Metals 7

TS 8th Class Physics 5th Lesson Metals and Non-Metals Intext Questions

Think and Discuss

Question 1.
What is the effect of humidity on quality of sound propagation? Is there any difference in propagation of sound in air during the summer and winter sessions? Discuss with your friends. (Text. P. No. 74)
Answer:
Generally sound travels faster in denser mediums. Therefore as humidity increases, the speed of sound also increases. There is no change in its amplitude and frequency. But quality of sound changes.

Question 2.
“Vibrations produce sound and sound produces vibrations”. Is it true? Discuss. (Text. P. No. 75) (Information skills/Conceptual understanding/Making hypothesis)
Answer:
“Vibrations produce sound and sound produces vibrations. The above statement is true.
Vibrations produce sound. But we are able to hear a sound of range 20 Hertz to 20,000 Hertz frequency. If the frequency is less than 20 Hz or more than 20,000 Hz we are unable to hear, even though they produce sound.

“Sound produces vibration”. The sound is produced by vibrating body. But all the vibrations produced by sounds have not much amplitude. So we are not able to observe the vibrations even though those sounds produce vibrations.

Question 3.
“Our ear has the three media through which sound propagates.” Discuss with your friends as to whether the above statement is true. (Information skills/Making hpo1hesWConceptual understanding)
Answer:
Our ear has the three media (solids liquid and gaseous) through which sound propagates.
Pinna of external ear collects the vibrations. They enter into the ear canal. Through this canal, (gaseous (air) state) sound propagates and strikes the tympanum (eardrum) and make it to vibrate. Eardrum and other parts are considered as solid state.

The vibrations from the oval window transmits to the cochlea which is the inner part of the ear. The cochlea is filled with fluid, which transmits the vibrations. Here the fluid is considered as liquid state. So the statement, “Our ear has three media through which sound propagates”, is correct statement.

TS 8th Class Physics 5th Lesson Metals and Non-Metals Activities

Activity – 1: Listening to sound and predicting its source: (Text. P. No. 65)

Question 1.
Prepare list of sounds heard and the sources from which they might have originated. (Project/Field investigations)
Answer:
I sit quietly for a while and listen the sound from my surroundings.

Sound heard Source of sound
1. Feeble barking Dog from some distance
2. Bell ringing Bell in school
3. Tick, Tick ……. From wall clock.
4. Tring, Tring … Phone in my house.
5. Gala Gala A few stones rattling in a metal box
6. Eela (whistling sound) A student has produced the sound from her/his mouth


Activity -2:

Identifying different sounds: (Text. P. No. 65)

Question 2.
How does the student at blackboard guess the source of sound without actually seeing the source?
Answer:
Already student is familiar with these sounds and sound travelled through air and reached his ear.

Questions based on the above Activity – 2

a. How do objects produce sound?
Answer:
Objects produce sound due to vibrations.

b. Sound is a part of our daily life. Do you agree? Discuss. Flow? (Daily life applications/information skill/Making hypothesis)
Answer:

  1. Throughout the day we are constantly exposed to different sounds.
  2. Examples are people talking, birds chirping, cries of animals, sounds of autos, motorbikes, buses, lorries, tractors, trains etc.
  3. Music played on loudspeakers at public places, televisions.
  4. Sound is an unavoidable and integral part of our lives. We are always surrounded by sound.
  5. Sound plays an important role in our lives. It helps us to communicate easily with each other.

c. What happens when objects made of metals are hit by a hammer or fall down from a height on a concrete floor?
Answer:
We will hear sound when objects made of metals are hit by a hammer or fall down from a height on a concrete floor.

TS 8th Class Physical Science Study Material 5th Lesson Metals and Non-Metals

d. How does a flute or a whistle produce sound?
Answer:
A flute or a whistle produces sound by making vibrations in air.

e. How would you feel if you touch a body while it is producing sound?
Answer:
feel their vibrations when I touch a body while it is producing sound.

Activity – 3:
VbratIne body produces sound: (Text. P. No. 66)

Question 3.
How do you prove that vibrating body produces sound?
(or)
Vibrating body produces sound. How do you prove this statement. (Project/Daily life applications! Experimentation)
Answer:

  • Take a metal plate. Fill It with some water and let the water settle.
  • Strike the brim of the plate with spoon. Observe the surface of water for waves on it.
  • You listen to the sound. Touch the metal plate. You can feel the vibrations.
  • From this we conclude that vibrating bodies produce sound.

TS 8th Class Physical Science Study Material 5th Lesson Metals and Non-Metals 8
Note: Students can write any activity given in page -67 in test book.

Questions based on the above Activity – 3

a. What have you observed while doing the above activities?
Answer:
When the object is vibrating then only we will be able to hear sound.

b. What changes took place in those objects?
Answer:
Objects will vibrate when they are producing sound.

c. How are they producing sound?
Answer:
The vibrating bodies produces sound

d. Is it possible to produces sound without vibration?
Answer:
No, it is not possible to produce sound without vibrations.

e. Does every vibrating body produce sound?
Answer:
No, every vibrating body does not produce sound.

f. Does sound has energy?
Answer:
Sound has energy.

Activity -4:
Sound has energy: (Text. P. No. 68)

Question 4.
How do you prove that sound has energy? (Experimentation & Field investigations)
Answer:

  • Take a plastic bottle and a cell phone. Cut the top of the bottle so that it looks like a glass.
  • Play songs on the mobile phone in high volume and place it in the bottle.
  • Close the mouth of the bottle with a balloon using rubber band. So that it covets the boule as shown in the figure and stretch it tightly so as to behave like a diaphragm.
  • Place some sugar crystals or some small sand particles and observe the movement of particles.
  • Do the sanie activity after removing the phone from the bottle.
  • When there is no cell phone inside the bottle, sand particles on diaphragm remain stationary.
  • With the cell phone playing songs inside the bottle, the diaphragm vibrates which can be seen through dancing of sand particles.
  • The sound produced by cell phone inside the bottle is responsible for these vibrations.
  • Thus sound has energy to make sand particles vibrate on the diaphragm.

TS 8th Class Physical Science Study Material 5th Lesson Metals and Non-Metals 9
Activity -5 :
Producing a sound that resembles sound of rainfall: (Text. P. No. 69)

Question 5.
How do you produce a sound that resembles sound of rainfall? (Appreciation! Field investigation/Aesthetic sense and values)
(or)
How do you appreciate your friend to his magic to produce a sound that resembles sound of rainfall with fingers?
Answer:

  1. My friend asked my classmates to start clapping with forefinger on left-hand palms.
  2. Then add middle finger and clap again. Lastly, add ring finger and then small finger successively and reverse the process gradually.
  3. All the students in our class did it simultaneously then the sounds produced resembled the rainfall.
  4. All of our students appreciated my friend for this activity.

Activity -6 :
Observing the changes in sound: (Text. P. No. 69)

Question 6.
How do you prepare a ‘Jalatarang’ musical instrument? What do you observe from it? (Model Making/Experimentation/Making hypothesis)
Answer:

  • Take 6 to 8 metal or glass bowls or tumblers.
  • Fill them with water in increasing order.
  • Strike gently each bowl or tumbler with a spoon.
  • Each tumbler produces different types of sound.
  • Now fill the bowls or tumblers with equal level of water.
  • Strike each bowl like in above case and listen to the sound.
  • Now every bowl produces same type of sound.
  • From this we can conclude that sounds are produced by the vibrating bodies and the air passes through orfices of the instruments.

TS 8th Class Physical Science Study Material 5th Lesson Metals and Non-Metals 10

Questions based on the above Activity – 6

a. What difference do you notice in the sound produced?
Answer:
There is a variation in the sound produced by the two cases.

b. Why there is variation in the sound produced due to change in the water level of a bowl?
Answer:
Due to the change in the heights of air levels they produce different sounds.

TS 8th Class Physical Science Study Material 5th Lesson Metals and Non-Metals

Activity -7:
Observing the movements of vocal cords during the speech: (Text. P. No. 71)

Question 7.
Describe an activity to observe the movement of vocal cords during the speech.
Answer:

  • Ask a friend to raise his neck up.
  • Stretch a chocolate wrapper across his mouth and ask him/her to blow air on the wrapper forcibly.
  • Observe the changes in movement at his/her throat.
  • Ask him/her now blow again slowly and observe the difference in movements.
  • During the first time the voice box gets tensed and produces high sound while the second time it is close to normal position of throat and produces lower sound.
  • The sound produced in above activity is due to the combination of vibrations produced in wrapper and the vocal cord.

Questions based on the above Lab Activity

a. Does sound travel only in air?
Answer:
No, sound travels in air, solids, Liquids.

b. Does it travel in any other gaseous medium?
Answer:
Yes. sound travels in other gaseous medium.

c. Does sound also travel in other media like solids and liquids?
Answer:
Yes, sound travels in other mediums like solids and liquids.

Activity -8:
Observing sound oropa8ation solid (Text. P. No. 72)

Question 8.
Describe an activity to show that sound travels in solids.
Answer:

  1. Take a metal or wooden strip. Strike it at one end and ask your friend to hear the sound by keeping his ears at the other end of the strip.
  2. Your friend heard the sound at the other end of the strip.
  3. Ask your friend to strike the table at one end and you listen to the sound produced Law keeping your ear on the other end of the table.
  4. You heard the sound from the table.
  5. From the above activities you can conclude that sound travels in solids like wood, metal etc.

TS 8th Class Physical Science Study Material 5th Lesson Metals and Non-Metals 11
Questions based on the above Activity-8

a. Are you able to hear the sound?
Answer:
Yes, we are able to listen the sound.

b. What is a median between you and your friend which is responsible for propagation of sound?
Answer:
The medium between me and my friend is solid.

c. Does sound travel in liquids?
Answer:
Yes, sound travels in liquids.

d. Can we hear the sound produced in water?
Answer:
Yes, we are able to listen the sound produced in water.

Activity – 9:
Propagation of sound through liquids (Text. P. No. 73)

Question 9.
How do you prove that sound travels through liquids? (Experimentation & Activity)
Answer:

  • Take a bucket or a bathtub.
  • Fill it with clean water.
  • Take two stones and strike them against each other keeping your hands inside the water.
  • Make sure that stones do not touch the body of the bucket.
  • place your ear gently on the water surface.
  • You hear the sound of striking stones.
  • It indicates the propagation of sound through water.
  • From the above activity, we conclude that sound travels through liquids.

Activity – 10:
Does the sound travel if there is no medium? (Text. P. No. 72)

Question 10.
How can you demonstrate that sound does not propagate through vacuum? (Experimentation/Daily life application/Field investigations)
Answer:

  • Take a water tumbler or glass. Make sure that the tumbler or glass is dry.
  • place cell phones small in size and play the ringtone of the mobile.
  • Listen to the ringtone and its volume level.
  • Cover the glass with a small plate and nd does no piopaate again listen to the ring tone and note the throush difference in volume of the sound.
  • Now suck the air from the glass kping it dosel to your mouth.
  • If you suck air quickly the rim of the glass stick around your mouth due to air lock.
  • Listen to the volume of the ringtone at this stage.
  • As you start sucking more and more air, the volume of the sound decreases gradually. If the air is sucked completely, you will not hear the sound at all.
  • From this activity we conclude that sound does not propagate through vacuum and it requires a medium.

TS 8th Class Physical Science Study Material 5th Lesson Metals and Non-Metals 12

Questions based on the above Activity – 10

a. Why are some sounds loud?
Answer:
Because the number of vibrations in one second are flore so we can hear sounds loud.

b. Why are some sounds feeble?
Answer:
Because the number of vibrations in one second are less compared to other.

c. Is there any relation between the intensity of sound and vibrations of the body which produces sound?
Answer:
Yes, there is a relation between the intensity of sound and vibrations of the body which producing sound. If vibrations of body increase intensity of sound increases.

Lab Activity – 1

Question 1.
How do you explain the relation between the intensity of sound produced by a body and the vibrations (amplitude) of the body? (Making hypothesis/Experinwntation/Field investigation)
Answer:
Aim: To know the relation between the intensity of sound produced by a body and the vibrators of the body.
Apparatus: Wooden table, hack-saw blade or metal scale of 30 cm long, and a brick.

Procedure:

  • Place the blade metal scale on the table with 10cm of the blade on the surface and rest of it in air.
  • Keep a heavy brick on one end of the blade which is kept on the table.
  • Vibrate the blade gently and observe the vibrations and simultaneously listen to the sounds.
  • Repeat the same, 2 – 3 times and record the observations in the table.
  • Now vibrate the blade using higher force. Observe the vibrations and listen to the sounds.
  • Repeat this for 2-3 times and record the observations.
Force Vibration of the blade scale Intensity of sound
Small force
Large force

From the above activity we conclude that as the force, increases the displacement as well as amplitude increases.
TS 8th Class Physical Science Study Material 5th Lesson Metals and Non-Metals 13

So when amplitude of sound increases, intensity of sound also increases.

Questions based on the above Lab Activity – 1

a. When do you hear a loud sound?
Answer:
When the scale is vibrating we can hear loud sound.

b. When do you hear a feebler sound?
Answer:
When the blade is vibrating we can hear feebler sound.

c. What difference do you notice in number of vibrations of blade / scale during loud and feeble sounds?
Answer:
Blade gives more vibrations while scale gives less vibrations in one second.

TS 8th Class Physical Science Study Material 5th Lesson Metals and Non-Metals

Lab Activity -2

How do you identify the pitch or shrillness of a sound?
(or)
What is the relation between pitch and frequency? (Experimentation/ Making hypothesis)
Answer:
Aim: Identifying pitch or shrillness of a sound. (or) Identify the relation between pitch and frequency.
Materials required: Wooden table, two hack-saw blades or metal scales of 30cm length and a brick.

Procedure:

  • Place the first blade on the table with 10cm portion of the blade on the table and rest of it in air.
  • Keep brick as weight on the 10cm portion of the blade which was kept on the table.
  • Place the second blade on the table, with 25cm on the table and 5cm in air, Keep brick as weight on the scale. See the gap between two blades be 10 cm.

TS 8th Class Physical Science Study Material 5th Lesson Metals and Non-Metals 14

  • Vibrate both the blades with same force. Observe the vibrations and listen to the sound produced.
  • Repeat the same 2-3 limes and record observations in the table.
Blade length in air Vibrations Sound
Blade-1:25cm
Blade -2: 10cm

You mas notice that the number of vibrations produced by 25cm long blade is less than the number of vibrations produced by 10cm long blade.
The Sound produced by 10cm blade is more shrill than that of 25cm blade.
The shrillness of a sound is known as pitch.
The number of vibrations per second is called frequency.
The pitch of the sound depends upon its frequency.
In the above experiment more is the shrill, more is the pitch and it has more frequency.
Thus the sound produced b)r a short blade (10cm) has high pitch and sound produced by (25cm) long blade has low pitch.

Questions based on the above Lab Activity

a. What difference do you notice in number of vibrations of two blades?
Answer:
We may notice that the number of vibrations produced are less in 25 cm long blade when compared to the vibrations of 10 cm long blade.

b. What difference do you notice in the quality of sound produced by them?
Answer:
The sound produced by 10 cm blade is more shrill when compared to that of 25 cm blade.

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