NDA/NA SOLVED PAPER 2015-I (GENERAL KNOWLEDGE)

Total Questions: 100

41. A solid is melted and allowed to cool and solidify again. The temperature is measured at equal intervals of time. The graph below shows the change of temperature with time.


The part of the curve that is practically horizontal due to

Correct Answer: (a) latent heat given away by the liquid
Solution:Latent heat is the energy absorbed or released at constant temperature per unit mass for change of state.

42. A deep sea diver may hurt his ear drum during diving because of

Correct Answer: (c) high water pressure
Solution:As you descend, water pressure increases, and the volume of air in your body decreases. This can cause problems such as sinus pain or a ruptured ear drum.

43. When you walk on a woolen carpet and bring your finger near the metallic handle of a door an electric shock is produced. This is because

Correct Answer: (a) charge is transferred from your body to the handle
Solution:All materials are made up of negatively- and positively-charged particles. These usually exist in equal amounts, balancing each other out. But when two materials come into contact, one may 'steal' negatively-charged electrons from the other. One material ends up with more negative charges than positive ones, meaning that it becomes negatively-charged overall, whilst the other becomes positively-charged. If the charges cannot move away as they are produced, they accumulate in the material as static charge, or electricity. Once you have built up a big enough static charge, an electric shock is almost inevitable. The moment you touch a conducting material such as metal, the excess electrons jump between your hand and the conductor, giving you a shock.

44. Which one among the following does not wet the walls of the glass vessel in which it is kept ?

Correct Answer: (c) Mercury
Solution:Mercury in a glass flask is a good example of the effects of the ratio between cohesive and adhesive forces. Because of its high cohesion and low adhesion to the glass, mercury does not spread out to cover the top of the flask, and if enough is placed in the flask to cover the bottom, it exhibits a strongly convex meniscus, whereas the meniscus of water is concave. Mercury will not wet the glass, unlike water and many other liquids, and if the glass is tipped, it will 'roll' around inside.

45. Permanent hardness of water is due to the presence of

Correct Answer: (b) sulphates of magnesium and calcium
Solution:Permanent hardness of water is usually caused by the presence of calcium sulfate and/or magnesium sulfates in the water.

46. In the reaction ZnO + C → Zn + CO, 'C' acts as

Correct Answer: (d) a reducing agent
Solution:'C' acts as a reducing agent in this reaction. A reducing agent is a substance that loses electrons, making it possible for another substance to gain electrons and be reduced. The oxidized substance is always the reducing agent.

47. Which of the following are the characteristics of organic farming?

1. Use of chemical fertilizers to improve soil fertility.
2. Frequent decomposing and fallowing.
3. Use of herbs to control pests.
4. Higher productivity per hectare.

Select the correct answer using the code given below :

Correct Answer: (c) 2 and 3 only
Solution:In organic farming, weed and pest control is based on methods like crop rotation, biological diversity, natural predators, organic manures and suitable chemical, thermal and biological intervention.

48. 'Yakuts' are the nomadic herders of

Correct Answer: (c) Tundra
Solution:Yakuts are the nomadic reindeer herder of Tundra.

49. A farmer in a semi-arid area claims that his farming practice is very environment friendly. Which of the following practices on his farm can justify his claim ?

1. Planting a tree belt.
2. Practising crop rotation.
3. Carrying out a large scale irrigation system.
4. Using organic fertilizers.

Select the correct answer using the code given below :

Correct Answer: (b) 1, 2 and 4
Solution:1, 2 and 4 are correct.

50. The luxuriant growth of natural vegetation in tropical rainforest is due to

1. fertile soil
2. hot and wet climate throughout the year.
3. intense sunlight for photosynthesis.
4. seasonal change to facilitate nutrient absorption.

Select the correct answer using the code given below:

Correct Answer: (b) 2 and 3 only
Solution:What makes humid tropical forests so productive is the combination of high temperatures, light, and rainfall year-round (good growing conditions) coupled with especially efficient nutrient recycling.