#Class 9

[vavaclasses]

NCERT Solutions- Sound class 9 notes

Introduction to Sound for Class 9 Science:

Sound is an intriguing and essential aspect of our daily lives, providing us with a rich sensory experience. In the realm of Class 9 Science, the study of sound delves into the fascinating world of vibrations, waves, and auditory sensations. Defined as a form of energy produced by the vibration of objects, sound plays a crucial role in communication, navigation, and even artistic expression through music. Understanding the characteristics of sound, its propagation through different mediums, and the phenomena of reflection and echo will unravel the mysteries of this dynamic and omnipresent force. As we embark on this scientific journey, we will explore the principles of sound, discovering how its various facets contribute to both practical applications and the beauty of our acoustic surroundings.

Sound:

Sound is a form of energy that produces a sensation of hearing in our ears.

It is produced by the vibration of objects, which create sound waves that travel through a medium (usually air).

Characteristics of Sound:

1. Pitch:

The highness or lowness of a sound is known as pitch.

Higher-frequency waves produce higher-pitch sounds, and lower-frequency waves produce lower-pitch sounds.

2. Loudness:

The amplitude of a sound wave determines its loudness.

Greater amplitude results in a louder sound.

3. Quality or Timbre:

It distinguishes between sounds of the same pitch and loudness produced by different sources.

It is affected by the harmonics and overtones in a sound.

Propagation of Sound:

Sound waves require a medium (solid, liquid, or gas) for propagation. They cannot travel through a vacuum.

Speed of sound varies with the medium. It is faster in solids, slower in liquids, and slowest in gases.

Reflection of Sound:

Sound waves follow the law of reflection, similar to light.

The angle of incidence is equal to the angle of reflection.

Echo:

An echo is a reflected sound that reaches the listener after bouncing off a surface.

The minimum distance required for hearing an echo is around 17.2 meters.

Uses of Multiple Reflections of Sound:

Stethoscope: Used by doctors to listen to internal sounds of the body.

Megaphones: Amplify sound by multiple reflections.

Whispering Galleries: Circular structures where sound waves reflect along the walls.

Ultrasound:

Sound waves with frequencies higher than the upper limit of human hearing (20,000 Hz) are called ultrasound.

Ultrasound is used in medical diagnostics (ultrasound imaging), cleaning delicate items, and industrial processes.

Applications of Sound Waves:

Sonar: Sound Navigation and Ranging is used for underwater navigation and communication.

Musical Instruments: Work based on the principles of sound production and resonance.

Speech Communication: Humans communicate using sound waves produced by their vocal cords.

NCERT- sound class 9 Important questions and answers

Here are some sample questions and answers related to the topic of sound for Class 9 Science:

1. What is sound?

Answer: Sound is a form of energy produced by the vibration of objects. It travels through a medium, usually air, and reaches our ears, producing the sensation of hearing.

2. Explain the three characteristics of sound.

Answer: The three characteristics of sound are pitch (highness or lowness), loudness (intensity), and quality or timbre (distinguishing feature of different sounds).

3. How does the pitch of a sound change with the frequency of the sound wave?

Answer: The pitch of a sound is directly related to the frequency of the sound wave. Higher frequency waves produce higher pitch sounds, while lower frequency waves result in lower pitch sounds.

4. Define echo.

Answer: Echo is a reflected sound that reaches the listener after bouncing off a surface. It occurs when the time interval between the original sound and its reflection is large enough to be perceptible.

5. Why does sound not travel in a vacuum?

Answer: Sound requires a medium (solid, liquid, or gas) for its propagation. In a vacuum, there is no medium, so sound waves cannot travel.

6. Explain the term 'ultrasound.'

Answer: Ultrasound refers to sound waves with frequencies higher than the upper limit of human hearing, which is 20,000 Hz. Ultrasound has various applications in medical diagnostics, cleaning, and industrial processes.

7. What is the minimum distance required to hear an echo?

Answer: The minimum distance required to hear an echo is approximately 17.2 meters.

8. How does the law of reflection apply to sound waves?

Answer: The law of reflection for sound waves states that the angle of incidence is equal to the angle of reflection. Sound waves reflect off surfaces in a manner similar to light waves.

9. Give an example of a practical application of ultrasound.

Answer: One practical application of ultrasound is in medical imaging, where it is used for procedures like ultrasound scans to visualize internal structures in the human body.

10. Name one musical instrument and explain how it produces sound.

Answer: One example is a guitar. The sound in a guitar is produced when the strings vibrate, creating sound waves. These waves are then amplified by the hollow body of the guitar, producing the audible sound.

Conclusion:

In conclusion, the study of sound in Class 9 Science has unravelled the captivating world of vibrations, waves, and the nuanced characteristics of this fundamental form of energy. From understanding the three primary features of sound—pitch, loudness, and quality—to exploring its propagation through different mediums and the intriguing phenomena of reflection and echo, students have delved into the intricacies of an omnipresent force in our daily lives.

This exploration extends beyond theoretical knowledge, offering insights into real-world applications such as sonar technology, medical diagnostics using ultrasound, and the functioning of musical instruments. As we conclude our journey through the science of sound, it becomes evident that sound is not merely a phenomenon perceived by our ears but a dynamic force with practical implications across various fields. The principles learned here lay the foundation for a deeper comprehension of acoustics and pave the way for a more profound appreciation of the role sound plays in our diverse and interconnected world.

[superchemistryclasses]

Learn the 2 Basic Differences Between Physical and Chemical Change Easily

We see many changes happening around us every day. Ice turns into water, wood burns, and food is cooked. These are all examples of different types of changes. But do you know how to tell which change is physical and which is chemical? In this article, we’ll understand the topic “Learn the 2 Basic Differences Between Physical and Chemical Change Easily” using very simple language and practical…

[sarthaks24]

Master Class 9 Maths & Science with Sarthaks

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NCERT Solutions for Class 9 Maths

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NCERT Solutions for Class 9 Science

Science is a fascinating subject, but it comes with its own set of challenges. Don’t worry! I’m here to make it easy and enjoyable for you. Our NCERT Solutions for Class 9 Science include:

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[applepixls]

Anyone else thinking about how odd the hermitcraft economy is?

in season 9 they had a minor economic recession after the diamond ore war because there were far too many diamonds in circulation making them (hypothetically) worth less than normal and ren stepped in as the king and did what has been done in the midst of a lot of irl economic depressions; he created a government so they could employ the policy of Keynesian economics (basically more gov't intervention to stabilize the economy, it mostly worked in 1930's japan!), he took control of diamonds and even introduced a new currency, royal emeralds (much like Germany after WW1! they had some hyperinflation because of the war reparations they had to pay and the gov't not understanding that printing more money makes the money worth less resulting in the mark [currency] being so worthless they started burning it because they couldn't afford wood for fires. a new gov't came into power and they replaced the mark with rentenmarks which did a lot of fixificating for the economy). Ren's gov't also introduced a lot of gov't funded projects like the quests (the irl equivalent for this would be Roosevelt's New Deal which introduced policies/projects called the Alphabet Agencies (among other things) such as the AAA, CCC, TVA (do you see why they're called the alphabet agencies?) that would adjust the value of grain so farmers could start earning money for produce again and create work that would support a growing economy, projects like building roads and bridges)

so basically, all the policies ren's government introduced were very logically sound and worked in real life to fix the economy (except that irl the Great Depression only fully ended because WW2 started-), the issue is that hermitcraft is not real life and hermits do not behave like real people, they behave like hermits.

lets start with the hermitcraft economy. unlike the real economy, hermits rarely adjust prices according to how many diamonds are "in circulation". i say this despite the fact grian in a recent-ish episode says that "everything costs more this season because diamonds are more common". that can't be true because the caves and cliffs update literally made diamonds more difficult to acquire. I will circle back to this point made by grian later

hermits not adjusting prices by server-wide abundance of diamonds (because they cant really know how much anyone has, much less the total amount of diamonds in circulation, they just know who has a lot and who is broke) means that more diamonds doesn't make them worth less like it did with German marks, it just means hermits have more expendable currency and can spend more money and less time gathering materials for projects. It is also notable that diamonds are constantly being added and taken out of circulation because they're an actual useful currency rather than real life currencies which are symbolic slips of paper. diamonds can be used for armour and tools and it can be acquired by mining. so because of how hermits spend money, taking diamonds out of the economy in s9 did nothing but make them poor and angry at the government. the hermitcraft economy is actually stronger with more diamonds in circulation and is worsened by gov't intervention.

so already the use of real life strategies is utterly useless in hermitcraft economy but there are a few other reasons as well

the hermits tendency to resist government as well as the flawed and greedy government itself are a couple but also the fact that all the hermits are self employed (in real life but also in universe). they own and stock their own shops meaning all profits are more or less direct; its not passed through hands of big corporations so the person producing the product gets mere cents. the hermits are essentially small business owners (which becomes a bit of a problem come season 10 but we're still talking about season 9). The important part is the self employment. the season 9 gov't introduces the quests which mimic and echo real life government funded projects but because they're all employed and the quests gave small amounts of diamonds back, they did very little for the hermits

I'm sure theres more to say but i think its time to move on to the very interesting season 10 economy

if you've missed it you must be living under a rock but hermits are all using permits this season meaning only one shop in the shopping district is selling any given item/material and as a result of this prices have gone sky high. at one point a single stack of mangrove logs cost 7 diamonds when in previous seasons you could get at least 1 stack of wood for 1 diamond if not more

So what is causing this economic depression and hyperinflation?

well, circling back to the point grian made about resources costing more because of abundance of diamonds, I would think it actually costs more because of the permits.

grian thinks the diamond prices are fair because he has middle of the road permits (and is one of the hermits who designed their shopping district, permit and economic system this season so he's biased), there is enough demand to keep him afloat when he's stocked but its nothing people are clamouring for and buying him out. on the other hand, joel made a lot of shops that no one shops at because his objectively weighted permits have not been selling as well as they anticipated when making the permits (also some people like etho and pearl have additional income from their not as fabulous permits because they've made a pay to play game to go with it) and finally there are hermits like mumbo whose gold, iron and item frame shops were constantly getting bought out so he was frustrated with trying to restock despite getting lots of profit

(another interesting dynamic to think about is permits like cleo's book permit which lost value as the season went on because everyone needed books early on but now that they're all playing late game Minecraft, everyone is pretty stocked up and buying from cleo less often)

Basically, grian is satisfied with the pricing because he's middle class and couldn't afford it if they were more expensive but appreciates not being constantly out of stock, joel is unsatisfied because he is lower class and never has enough expendable currency to fund his projects because materials are too expensive and his permits aren't worth enough to sell them for more, and mumbo is unsatisfied because he is higher class and is constantly out of stock because his materials sell out too often and he wants to sell them for more to stay in stock more (classic supply and demand, he doesn't want to stock them as often making the supply lower and the demand proportionally higher making them worth more and therefore more expensive)

the reason i say the permits are to blame for the high prices is because they cause the responsibility of constantly stocking something to fall on one person (in past seasons, if one persons sandstone shop was out of stock you could go check someone else's sandstone shop). the threat of taking the permit away if they arent stocked along with the difficulty of constantly stocking some of these materials raises the cost.

a great example of this is skizzleman because his mangrove and cherry wood shop was one of the first shops to be built in the shopping district, meaning he somewhat set the prices this season. now, mangrove and cherry are both difficult trees to harvest because of their unconventional shapes and the fact that they are more recent additions (and skizz's stubborn desire to design his own farms...) so because of the time required to gather them the prices already were hitched up. add that to the fact that they are trying to constantly be in stock and therefore low prices that allow hermits to completely buy out the shops are unfavourable, and you get sky rocket-ing prices. (it is also difficult because skizz had no prior experience with hermitcraft pricing)

in conclusion... hermitcraft needs a laissez-faire economy (f. a. hayek) to function and not go into economic depression. Between the nature of the diamond currency, hermits' tendency to rebel against governments, the way they use the concept of supply and demand to price their goods, and the restrictions permits put on supplying products, hermits have proven that extensive structure and government intervention have not improved economic wellbeing the way that it does in real life

thus, hermits do not behave like regular humans, they operate on fae laws of its funny so lets do it and therefore must be governed as such (aka not governed), thank you for coming to my ted talk

[floccinaucinihilipilificationa]

[rubbish78]

Hugh Jackman as Wolverine/Logan Howlett shirtless moments

[galaxycoachingclasses]

Splitting the Middle Term in Easy Way Short Trick for splitting the midd...

[akiacia]

maggie lore post

[cyber-seaweed]

soras side of chain of memories represents comphet and how harmful it is to push heterosexuality on young queer people. rikus side of chain of memories represents internalized homophobia and how you can become your own worst enemy when conditioned at a young age to feel disgusted by your own sexuality. this is why soras side is literally about gaslighting him into thinking that romantic memories he made with another male character were changed into a female character, and why rikus is so heavily focused on learning not to fear the feelings hidden within his heart.

[2129888]

[vavaclasses]

Study Notes on The French Revolution Class 9

Introduction to the French Revolution Class 9

The French Revolution, which began in 1789, was a period of radical social and political upheaval in France. It marked the decline of absolute monarchies, the rise of secular and democratic republics, and the eventual rise of Napoleon Bonaparte. This revolutionary period is crucial in understanding the transition from feudalism to modernity in Europe.

Causes of the French Revolution

1. Social Inequality:

French society was divided into three estates: the First Estate (clergy), the Second Estate (nobility), and the Third Estate (commoners). The Third Estate, despite being the majority, bore the brunt of taxation and had little political power.

2. Economic Hardship:

France's involvement in costly wars, including the American Revolution, and lavish spending by King Louis XVI and his predecessors had drained the treasury. This led to increased taxes on the already burdened Third Estate.

3. Political Mismanagement:

King Louis XVI’s inability to manage the state’s finances and his failure to address the grievances of the people exacerbated the situation.

4. Enlightenment Ideas:

Enlightenment thinkers like Voltaire, Rousseau, and Montesquieu criticized the existing social and political structures and promoted ideas of liberty, equality, and fraternity.

Key Events of the French Revolution

1. Meeting of the Estates-General (May 1789):

King Louis XVI called a meeting of the Estates-General to address the financial crisis. The Third Estate, frustrated with their lack of representation, broke away and declared themselves the National Assembly.

2. Tennis Court Oath (June 1789):

Members of the Third Estate took an oath to not disband until a new constitution was created. This was a significant step towards the establishment of a representative government.

3. Storming of the Bastille (July 14, 1789):

The storming of the Bastille, a symbol of the king’s tyranny, marked the beginning of the French Revolution. It is celebrated as France’s National Day.

4. The Great Fear (July-August 1789):

A period of panic and riot by peasants and others amid rumors of an aristocratic conspiracy to overthrow the Third Estate. This led to widespread violence and the eventual abolition of feudal privileges.

5. Declaration of the Rights of Man and of the Citizen (August 1789):

This document proclaimed the equality of all men, the sovereignty of the people, and the rights to liberty, property, security, and resistance to oppression.

6. Women's March on Versailles (October 1789):

Thousands of Parisian women marched to Versailles, demanding bread and forcing the royal family to move to Paris, signaling the shift of power from the monarchy to the people.

7. Formation of the Legislative Assembly (1791):

A new legislative body was formed, creating a constitutional monarchy. However, this did not satisfy all revolutionary factions.

8. Reign of Terror (1793-1794):

Led by Robespierre and the Committee of Public Safety, this period was marked by mass executions of perceived enemies of the revolution.

9. Rise of Napoleon Bonaparte (1799):

Napoleon’s coup d’état on November 9, 1799, ended the revolution, leading to his rise as the First Consul and eventually Emperor of France.

Impact of the French Revolution

1. End of Feudalism:

The revolution led to the abolition of feudal privileges and the establishment of a more egalitarian society.

2. Spread of Revolutionary Ideas:

The principles of liberty, equality, and fraternity inspired subsequent revolutions and movements across Europe and the world.

3. Changes in Governance:

The revolution paved the way for the rise of democratic republics and the decline of absolute monarchies.

4. Economic Reforms:

The confiscation of church lands and redistribution of property contributed to the restructuring of the French economy.

5. Napoleonic Code:

Napoleon’s establishment of a uniform legal code influenced legal systems worldwide.

Conclusion

The French Revolution was a turning point in world history. It dismantled the old social and political structures and laid the foundation for modern democratic institutions. Understanding the causes, key events, and impacts of the French Revolution is crucial for students to grasp the evolution of contemporary societies and political systems.

French Revolution Class 9 Summary of Key Points

Causes: Social inequality, economic hardship, political mismanagement, Enlightenment ideas.

Key Events: Estates-General, Tennis Court Oath, Storming of the Bastille, Great Fear, Declaration of the Rights of Man, Women’s March on Versailles, Legislative Assembly, Reign of Terror, rise of Napoleon.

Impact: End of feudalism, spread of revolutionary ideas, changes in governance, economic reforms, Napoleonic Code.

These notes provide a comprehensive overview of the French Revolution, highlighting its significance in shaping modern political and social landscapes.

[isatohlee]

Solace

Song: Hijo Del Corazón

@c-lunette

[kabukiaku]

dug up a wip I had of the young emeritus brothers + young primo!! I tweaked just a bit. ❤️💚💜

[l3v5ha]

#SEVERANCE: [ i'm a busy woman ... ]