SOLVED PAPER 2021 (CDS) (I) (General Awareness)

Total Questions: 120

111. Which one among the following is a free living animal ?

Correct Answer: (d) Planaria
Solution:Planarian, any of a group of widely distributed, mostly free-living flatworms of the class Turbellaria. Rest options are patasites.

112. Which one of the following is the structure of a cardiac muscle cell ?

Correct Answer: (d) Cylindrical, Branched and Uninucleate
Solution:Cardiac muscles are branched, cylindrical, Involuntary and uninucleated. It constitutes the main tissue that mades the wall of the heart. They are uninucleate as each cell has a single nucleus. Also, these cells are not controlled by our will and hence said to be involuntary.

113. Which one of the following naturally occurring acids is found in abundance in tomato ?

Correct Answer: (b) Citric acid
Solution:Citric acid is the most abundant organic acid in tomatoes with some malic acid also present.

114. Which one of the following is used in soda-acid fire extinguishers

Correct Answer: (b) Sodium hydrogen carbonate
Solution:Soda-acid fire extinguisher contains a solution of sodium hydrogen carbonate (NaHCO₃) and sulfuric acid (H₂SO₄). The following reaction takes place :

2NaHCO₃ + H₂SO₄ → Na₂SO₄ + 2H₂O + 2CO₂

This increases the percentage of carbon dioxide in air. Due to this, the supply of air is cut off and fire is extinguished.

115. Which one of the following sodium compounds is used for softening hard water?

Correct Answer: (a) Na₂CO₃
Solution:The sodium compound which is used for softening hard water is called sodium carbonate which is most commonly known as washing soda (Na₂CO₃ . 10H₂O) It is prepared by heating baking soda and then recrystallising the product so obtained to get washing soda.

116. Calcium oxide reacts vigorously with water to produce slaked lime whose solution is used for white-washing walls. This slaked lime reacts with component (A) in air to form a thin layer of component (B) to give a shiny finish. What are the components (A) and (B)?

Correct Answer: (d)
Solution:A solution of slaked lime [Ca(OH)₂ ] is used to white wash the walls. Calcium hydroxide reacts with the carbon dioxide (A) in air to form than layer of calcium carbonate [(CaCO₃) (component B)] on the walls. It gives a shiny finish to the walls.

117. How many internal reflections of light take place in the formation of primary rainbow?

Correct Answer: (b) 1
Solution:A rainbow is regarded as one of the most spectacular light shows observed on the earth. A rainbow is a multicoloured arc formed by light striking water droplets. Rainbows are created after rain by the reflection, refraction, and dispersion of light in water droplets. All of these events produce a light spectrum in the sky, which is known as a rainbow. In Primary Rainbow, one total internal reflection and two refractions of white light by water droplets produce the primary rainbow.

118. The direction of acceleration in uniform circular motion is along the

Correct Answer: (d) direction perpendicular to velocity.
Solution:Uniform circular motion can be described as the motion of an object in a circle at a constant speed. As an object moves in a circle, it is constantly changing its direction. Accelerating objects are objects which are changing their velocity -either the speed (i.e., magnitude of the velocity vector) or the direction. An object undergoing uniform circular motion is moving with a constant speed. Nonetheless, it is accelerating due to its change in direction.. The direction of the acceleration is inwards.

119. The weight of an object is due to

Correct Answer: (c) the force that it exerts on the ground.
Solution:The weight of an object is nothing but the gravitational force with which it is attracted towards the center of the Earth, It also define as the magnitude of the reaction force exerted on a body by mechanisms that counteract the effects of gravity: the weight is the quantity that is measured by, for example, a spring scale.

120. The size of particles being studied in 'nano-technology' is about

Correct Answer: (b) 1 — 100nm
Solution:The correct answer is 1 - 100 nm. Nanoparticle, ultrafine unit with dimensions measured in nanometers (nm; 1nm = 10 - 9 metre). Nanoparticles exist in the natural world and are also created as a result of human activities.