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Mach Number

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Mach Number

Consider the following statements:

Hypersonic flow regime is accompanied with Oblique Shock Waves.
The speed of sound varies from planet to planet.
Mach number appears as similarity parameter in equations of compressible flow.

Choose the correct answer from the code given below:

	A	1 and 2 only

	B	2 and 3 only

	C	1, 2 and 3

	D	1 and 3 only

Your Ans is

Right ans is C

Your Answer Is Correct

Your Answer Is Wrong

Explanation :

The Mach number depends on the speed of sound in the gas and the speed of sound depends on the type of gas and the temperature of the gas. Thus the speed of sound varies from planet to planet.
Hypersonic flow regime is often accompanied with Oblique Shock Waves.
If one looks into the equations of compressible flow of gases, Mach number appears in the similarity parameter.

Related Question

Biofuels

Consider the following pairs with reference to the categories of biofuels:

First Generation Biodiesel: produced from sugar, starch, vegetable oil
Second Generation Biofuels: produced from non-food crops
Third Generation Biofuels: require cultivable/arable land for production
Fourth Generation Biofuels: crops are genetically engineered to take in high amounts of carbon

Which of the pair(s) is/are correct?

	A	1, 2 and 3

	B	2, 3 and 4

	C	1,2 and 4

	D	1, 2, 3 and 4

Your Ans is

Right ans is C

Your Answer Is Correct

Your Answer Is Wrong

Explanation :

Context: Recently, Stardust 1.0 has been launched from USA, which became the first commercial space launch powered by biofuel.

Explanation:

Biofuels

Any hydrocarbon fuel that is produced from an organic matter (living or once living material) in a short period of time is considered a biofuel.
Biofuels may be solid, liquid or gaseous in nature.

First Generation Biofuels

Fuels produced from sugar, starch, vegetable oil, or animal fats utilizing conventional technology.
Examples: Bioalcohols, Biodiesel, Vegetable Oil, Bioethers, Biogas.

Second Generation Biofuels

Fuels made from non-food crops such as cellulosic biofuels and waste biomass i.e. stalks of wheat and corn, and wood).
Example: cellulose ethanol

Third Generation Biofuels

Fuels made from micro-organisms such as algae.
It doesn’t require cultivable/arable land for production.
Example: Butanol

Fourth Generation Biofuels

In the production of these fuels, crops that are genetically engineered to take in high amounts of carbon are grown and harvested as biomass.
The crops are then converted into fuel using second generation techniques.
Like the third generation, fourth-generation biofuels are made using non-arable land. However, unlike the third, they do not need the destruction of biomass.
Examples: electrofuels and photo-biological solar fuels

BeiDou Navigation Satellite System

Recently, which of the following country formally launched its Navigation Satellite System under the name BeiDou?

	A	China

	B	Russia

	C	Japan

	D	None of the above

Your Ans is

Right ans is A

Your Answer Is Correct

Your Answer Is Wrong

Explanation :

China has completed its BeiDou Navigation Satellite System constellation, coming up with a product that can potentially rival the US Global Positioning System (GPS).
China initiated BeiDou in 1994 with aims to integrate its application in different sectors, including fishery, agriculture, special care, mass-market applications, forestry and public security.
The name BeiDou comes from Chinese word for the Big Dipper or Plough constellation.
It consists of 27 satellites in medium Earth orbit, five in geostationary orbit and three more in inclined geosynchronous orbits.
The navigation satellite system was completed in three steps: BDS-1 which provided services to China, BDS- 2 to provide services to the Asia-Pacific region and BDS-3 which provides services worldwide.
China’s navigation system uses a network of satellites and can provide positional accuracies of under ten meters (GPS provides positioning accuracies of under 2.2 meters).
BeiDou offers services including accurate positioning, navigation and timing as well as short message communication.

Other Countries’ Navigation Systems

The GPS is owned by the US government and operated by the US Air Force.
Apart from this, Russia has its navigation system called GLONASS, the European Union (EU) has Galileo, while India’s is called Navigation with Indian Constellation (NavIC).

Xenobots

Recently, scientists in the United States have created the world’s first living machines- Xenobots, tiny robots that can move around on their own. Which of the following animal’s cell was used in making the Xenobots?

	A	African Clawed Frog

	B	Electric Catfish of Nile

	C	Gambian Pouched rat

	D	Cape Dwarf Gecko

Your Ans is

Right ans is A

Your Answer Is Correct

Your Answer Is Wrong

Explanation :

Scientists in the United States have named the millimetre-wide robots Xenobots (world’s first living machines) — after the species of aquatic frog found across sub-Saharan Africa from Nigeria and Sudan to South Africa,Xenopus laevis.
Scientists have repurposed living cells scraped from frog embryos and assembled them into entirely new life-forms.

Application

The xenobots can move toward a target, perhaps pick up a payload (like a medicine that needs to be carried to a specific place inside a patient) — and heal themselves after being cut.

Microdot Technology

Consider the following statements with reference to the Microdot Technology:

Microdot technology involves spraying the body and parts of the vehicle or any other machine with microscopic dots, which give a unique identification.
The microdots and adhesive will become permanent fixtures/affixation which cannot be removed without damaging the asset i.e. the vehicle itself.

Choose the correct answer from the codes given below:

	A	Only 1

	B	Only 2

	C	Both 1 and 2

	D	Neither 1 nor 2

Your Ans is

Right ans is C

Your Answer Is Correct

Your Answer Is Wrong

Explanation :

Microdot Technology involves spraying thousands of the small dots laser etched with a PIN (Personal Identification Number) number, linked to the Vehicle Number, throughout the vehicle. As the polymer dots are 1mm by 1mm it is impossible to locate them.
These can be read physically with a microscope and identified with an ultraviolet light source.
The microdots and adhesive fix permanently and cannot be removed without damaging the vehicle itself.

Advantages

A vehicle, which has microdots sprayed on its body, if stolen, can be easily identified with the help of this technology.
Similarly, the use of fake spare parts can also be prevented as counterfeit ones can be singled out easily.

Uranium Enrichment

Recently, Iran resumed uranium enrichment at its underground Fordow plant located near Tehran.Consider the following given statements about the uranium enrichment process:

Uranium needs to be in a solid form for enrichment due to the varying chemical and physical properties the different isotopes (U-235 and U-238).
Enriched uranium is produced by feeding uranium hexafluoride gas into centrifuges to separate out the most suitable isotope for nuclear fission, called U-235.

Choose the correct answer from the codes given below:

	A	Only 1

	B	Only 2

	C	Both 1nad 2

	D	Neither 1 nor 2

Your Ans is

Right ans is B

Your Answer Is Correct

Your Answer Is Wrong

Explanation :

Natural uranium is composed of various isotopes, or different types of uranium. It contains approximately 99.3% of the isotope uranium-238, and has only very small concentrations, about 7%, of the fissile isotope uranium-235. An isotope is considered fissile if it can be split by a slow moving neutron.
Uranium-235 is the most significant fissile isotope of uranium for reactor fuel and nuclear weapons.
Uranium needs to be in a gaseous form for enrichment due to the varying chemical and physical properties the different isotopes (U-235 and U-238) have.
Commercially, the U235 isotope is enriched to 3 to 5% (from the natural state of 0.7%) and is then further processed to create nuclear fuel.
At the conversion plant, uranium oxide is converted to the chemical form of uranium hexafluoride (UF6) to be usable in an enrichment facility.

Stages of Enrichment

Uranium enriched to concentrations above 0.7% but less than 20% uranium-235 is defined as low enriched uranium (LEU). Most nuclear reactors use LEU that is about 3-5% uranium-235.
Uranium enriched to more than 20% uranium-235 is defined as highly enriched uranium (HEU). All HEU is weapons-usable, but the lower the enrichment level the greater the amount of material required to achieve a critical mass - the amount of material required to build a bomb.
States with nuclear weapons typically use so-called weapons-grade HEU, which is typically defined as 90% HEU or above, to minimize weapons’ size.

Gravitational Lensing

Recently, researchers plan to investigate how new stars are born using NASA’s James Webb Space Telescope. For this, they will take the help of a natural phenomenon called Gravitational Lensing. Consider the following statements regarding the gravitational lensing:

The phenomenon occurs when a huge amount of matter, such as a massive galaxy or cluster of galaxies, creates a gravitational field that distorts and magnifies the light from objects behind it, but in the same line of sight.
The investigation is a part of the programme called Targeting Extremely Magnified Panchromatic Lensed Arcs and Their Extended Star Formation (TEMPLATES).

Choose the correct answer from the codes given below:

	A	Only 1

	B	Only 2

	C	Both 1 and 2

	D	None of the above

Your Ans is

Right ans is C

Your Answer Is Correct

Your Answer Is Wrong

Explanation :

Gravitational lensing occurs when a huge amount of matter - a galaxy cluster, for example - creates a gravitational field that magnifies light from objects behind it.
The Milky Way today forms the equivalent of one Sun every year, but in the past, that rate was up to 100 times greater. NASA now plans to look billions of years into the past in order to understand how our Sun formed.
The NASA program aimed at using gravitational lensing via its James Webb telescope(scheduled to launch in 2021) is called Targeting Extremely Magnified Panchromatic Lensed Arcs and Their Extended Star Formation (TEMPLATES). So, both the given statements are correct.

Source:Civil Services Chronicle Online

Cryptocurrency

Consider the following statements with respect to Cryptocurrency:

It is a form of digital cash that uses encryption technology to make it secure.
People can store their cryptocurrency stashes in virtual wallets.
Cryptocurrency is powered by a technology called blockchain, which functions like an open ledger that gets updated in real time.
Cryptocurrency is secure and non-anonymous.

Select the correct answer using the code given below:

	A	1, 2, 3 and 4

	B	1, 2 and 3

	C	2, 3 and 4

	D	1, 3 and 4

Your Ans is

Right ans is B

Your Answer Is Correct

Your Answer Is Wrong

Explanation :

It is a form of digital cash that uses encryption technology to make it secure. Cryptocurrencies exist not as physical bills or coins but rather as lines of digitally signed computer code. Records are typically kept on ledgers known as blockchain. People can store their cryptocurrency stashes in virtual wallets that resemble online bank accounts. Cryptocurrency is supposed to be secure and anonymous.

Global Clusters

Which of the following can best describe global clusters?

	A	It is a collection of different galaxies.

	B	It is a collection of stars with a variety of masses but with similar chemical composition.

	C	It is a collection of asteroids and meteors between Mars and Jupiter.

	D	It is a collection of habitable planets in goldilocks zone.

Your Ans is

Right ans is B

Your Answer Is Correct

Your Answer Is Wrong

Explanation :

Globular clusters are collections of thousands to millions of stars, moving as one unit.

Source: CSC May 2019

Solar Tsunami

Consider the following statements with respect to Solar Tsunami:

The Sun’s magnetic field, from which sunspots gets generated, wraps around the sun in the east-west direction.
At the end of a solar cycle, magnetic dam can break, releasing huge amounts of plasma cascading like a tsunami towards the equator.
The tsunami waves travel at high speeds of about 1,000 km per hour carrying excess plasma to the upper-latitudes.

Select the correct answer using the codes given below:

	A	1 and 3

	B	Only 1

	C	1, 2 and 3

	D	2 and 3

Your Ans is

Right ans is B

Your Answer Is Correct

Your Answer Is Wrong

Explanation :

Statement 1 is correct: The Sun’s magnetic field, from which sunspots gets generated, wraps around the sun in the east-west direction.
Statement 2 is incorrect: At the end of a solar cycle, this magnetic dam can break, releasing huge amounts of plasma cascading like a tsunami towards the poles. Statement 3 is incorrect These tsunami waves travel at high speeds of about 1,000 km per hour carrying excess plasma to the mid-latitudes.

Source: CSC May 2019

Dark Matter

Which of the following statements are correct with respect to Dark Matter?

Dark Matter emits no light and cannot be seen directly
Dark Matters are stars or planets.
Astronomers do not detect gamma rays produced by them.
Dark matter is black hole.

Select the correct answer using the codes given below:

	A	2, 3 and 4

	B	1, 3 and 4

	C	1 and 3

	D	1, 2, 3 and 4

Your Ans is

Right ans is C

Your Answer Is Correct

Your Answer Is Wrong

Explanation :

Statement 1 is correct because dark matter emits no light and is not visible directly, so it cannot be stars or planets.
Statement 2 is incorrect.
Statement 3 is incorrect as Antimatter annihilates matter on contact, producing gamma rays. Astronomers do not detect them. Statement 4 is correct because Dark matter is not black hole.

Source: CSC May 2019

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