Question Discussion & Solution

CONCEPT:

Equilibrium of a rigid body:

• A rigid body is said to be in mechanical equilibrium if both its linear momentum and angular momentum are not changing with time, or equivalently, the body has neither linear acceleration nor angular acceleration.
• Condition for the mechanical equilibrium:
  1. The total force, i.e. the vector sum of the forces, on the rigid body is zero.
  2. The total torque, i.e. the vector sum of the torques on the rigid body is zero.

⇒ \(\rm\vec{F_1}+\vec{F_2}+...+\vec{F_n}=0\)

⇒ \(\rm \vec{τ_1}+\vec{τ_2}+...+\vec{τ_n}=0\)

• If the forces on a rigid body are acting in the 3 dimensions, then six independent conditions to be satisfied for the mechanical equilibrium of a rigid body.
• If all the forces acting on the body are coplanar, then we need only three conditions to be satisfied for mechanical equilibrium.
• A body may be in partial equilibrium, i.e., it may be in translational equilibrium and not in rotational equilibrium, or it may be in rotational equilibrium and not in translational equilibrium.

EXPLANATION:

• A rigid body is said to be in mechanical equilibrium if both its linear momentum and angular momentum are not changing with time, or equivalently, the body has neither linear acceleration nor angular acceleration.
• We know that the linear acceleration and the angular acceleration of a stationary body are zero.

A book is kept on a table:

• In this case, the book will be stationary so it is an example of the equilibrium of a body.

A ball is moving downward freely under gravity:

• We know that when a ball moves freely under gravity, then only the gravitational force will act on the ball due to which the ball accelerates downward.
• Therefore ball is moving downward freely under gravity is not an example of the equilibrium of a body.
• Hence, option 1 is correct.

The correct answer is Three.

According to the Dowry Prohibition Act, 1961, 3 conditions related to dowry have been stated.

Key Points

Dowry Prohibition Act, 1961

• Dowry Prohibition Act, Indian law, enacted on May 1, 1961, intended to prevent the giving or receiving of a dowry.
• Under the Dowry Prohibition Act, dowry includes property, goods, or money given by either party to the marriage, by the parents of either party or by anyone else in connection with the marriage.
• There are three occasions related to dowry.
  • One is before the marriage,
  • The second is at the time of marriage 
  • The third is at any time after the marriage. The third occasion may appear to be an unending period. But the crucial words are in connection with the marriage of the said parties.

The correct answer is Dot Matrix.

Important Points

• Impact printer
  • Impact printer refers to a class of printers that work by banging a head or needle against an ink ribbon to make a mark on the paper.
  • The three most common forms of impact printers are:
    • Dot-matrix.
    • Daisy-wheel.
    • Line printers.

Key Points

• Dot-matrix Printers 
  • The technology behind dot-matrix printing is in such a way that the paper is pressed against a drum (a rubber-coated cylinder).
  • The electromagnetically-driven printhead moves across the paper and strikes the printer ribbon situated between the paper and printhead pin.
  • The impact of the printhead against the printer ribbon imprints ink dots on the paper which create human-readable characters.

Additional Information

• Laser Printer
  • ​A laser printer is a printer that uses a focused beam of light to transfer text and images onto paper. 
• Inkjet printer
  • ​Inkjet printers, as the name implies, use ink to print text, graphics, and images onto various types of paper. 
  • Inkjet printers, cartridges, and supplies are more widely available therefore cheaper than their thermal printer.
• Thermal printer​
  • Thermal printers use tiny heating elements to activate or transfer pigments.
  • Thermal printers are used most commonly to create labels, safety signs.

The correct answer is ALGORITHM.

Key Points

• An algorithm is a specific procedure for solving a well-defined computational problem.
• The development and analysis of algorithms are fundamental to all aspects of Computer Science like AI, databases, graphics, networking, OS, etc.
• Algorithm development is more than just programming.
  • It requires an understanding of the alternatives available for solving a computational problem.
  • It includes the hardware, networking, programming language, and performance constraints that accompany any particular solution.

Additional Information

• An official language comprising a collection of instructions that produce different kinds of output is a programming language.
• In computer science, programming languages are used to implement algorithms.
• Most of the languages of programming consist of computer instructions.

CONCEPT:

• Electric Power: The rate at which electrical energy is dissipated into other forms of energy is called electrical power i.e.,

\(P = \frac{W}{t} = VI = {I^2}R = \frac{{{V^2}}}{R}\)

Where V = Potential difference, R = Resistance and I = current.

EXPLANATION:

• Mathematically power can be written as,

\(\Rightarrow P = \frac{W}{t} = VI \)

If, W = 1 J and t = 1 sec, then P = 1 watt

• Thus the power of an electric circuit is said to be one watt or 1 ampere - volt if one joule of energy is consumed in one second. Therefore option 1 is correct.