Question Discussion & Solution

Explanation:

• Bronze is an alloy of copper and tin as the two main constituent elements.
• Bronze is a copper-based alloy that typically consists of approximately 88% copper and 12% tin.
• Some other elements added in minute quantities can be aluminium, nickel or zinc.
• It is one of the first alloys used by mankind and an entire era known as the 'Bronze Age' is known because of the extensive use of the alloy in many human artefacts.

Additional Information

Steel: 

• Stainless steel is an alloy of iron and chromium.
• Steel is an alloy of iron and carbon.
• Stainless steels are steels containing at least 10.5% chromium, less than 1.2% carbon, and other alloying elements.

Solder:

• Soldering is a joining process used to join different types of metals together having different properties. 
• Solder is a metal alloy, usually made up of tin and lead which is melted using a hot iron (soldering iron).
• The iron is heated to temperatures above 600˚F which then cools to create a strong bond.
• Flux material used in soldering is ZnCl2 (Zinc Chloride) and NH4Cl (Ammonium Chloride).

Brass:

• Brass is a metal alloy that is made up of copper and zinc.
• The proportions of zinc and copper can vary to create different types of brasses with different properties.
• It has higher malleability than bronze or zinc and has a relatively low melting point (900 to 940 °C).

Mistake Points

• Copper was the first metal used by men.
• Copper was first used by man over 10,000 years ago.  
• Probably copper can be found as a naturally occurring native metal that is sometimes found in large lumps on the ground.
• People learned to make this into copper tools and other things, although, for a metal, it is quite soft.
• When it was melted over the fire, people learned how to make an alloy called bronze, which is much harder and stronger than copper.

The variable is the basic unit of storage in a Java program. A variable is defined by the combination of an identifier, a type, and an optional initializer.

Variable names cannot be keyword, it is case- sensitive and the first character must be a letter.

In Java, all variables must be declared before they can be used. The basic form of a variable declaration is:

type identifier [ = value ][, identifier [= value ] …];

Examples:

int a, b;

int a = 10, b = 20, c = 30;

int a, b = 20, c;

Confusion point

In Java, variable name can also start with underscore character “_”, or a dollar sign “$”.

Best Possible answer is chosen.

The correct answer is option 4) i.e. kg-1 m2

CONCEPT:

• Gravitational constant, G: G is a physical constant and therefore is universal in nature and has a constant value everywhere.
  • The value of G does not change with respect to time or place and is equivalent to 6.674 × 10-11 N m2 kg-2
  • The SI unit of G is N m2 kg-2
• Acceleration due to gravity, g: It is the acceleration of a body due to the force exerted from the earth's gravity.
  • It has a constant value of 9.8 m/s² within the surface of Earth.
  • The SI unit of g is m s^-2

EXPLANATION:

The unit of G = N m2 kg-2 = (mass × acceleration)m2 kg-2 = (kg × m/s²)m2 kg-2     (∵ N is the SI unit of force)

The unit of g = m s^-2​

Ratio, \(\frac{G}{g} = \frac{m^3 kg^{-1 }s^{-2 }}{m s^{-2}} =\) kg-1 m2

CONCEPT:

• Plane mirror: This mirror is straight without any inward or outward curve.
  • It forms a virtual image and upright image which is of size as same as the object.
  • The bathroom mirrors are an example.
• Concave mirror: The mirrors curved inside on the reflecting side are called concave mirrors.
  • These mirrors produce a real, inverted, and magnified image of the object.
  • These are used in reflecting telescopes, shaving mirrors, and ophthalmoscope.

• Convex mirror: It is an outward curved mirror that produces a diminished image.
  • Convex mirrors either diverge a parallel beam of light into all directions or gather light from all directions and produce a parallel beam out of it.

EXPLANATION:

• Following are the reasons as to why a convex mirror is used as a rearview mirror in the vehicle

• The image formed by the convex mirror is virtual and erect in contrast to that of the real but inverted image of the concave mirror.
• It gathers light from all directions and aligns it as a parallel beam so that it provides a wider view to the viewer. That's why the convex mirror is used as a rear-view mirror in vehicles. So option 2 is correct.

• In 1837, Charles Babbage proposed the first general mechanical computer, the Analytical Engine; The Analytical Engine contained an ALU (Arithmetic Logic Unit), basic flow control, punch cards, and integrated memory
• Charles Babbage is credited with inventing the first mechanical computer that eventually led to more complex electronic designs, though all the essential ideas of modern computers are to be found in Babbage's analytical engine; Hence regarded as the father of computer science
• Blaise Pascal (1623 – 1662) was a French mathematician, physicist, inventor, writer and Catholic theologian
• John Napier (1550 – 1617) was a Scottish landowner known as a mathematician, physicist, and astronomer; He is best known as the discoverer of logarithms