Option “4” is correct. The escape velocity of earth is 11.2 km/sec.
392. What is measured by manometer?
1. Air pressure
2. Pressure of gas
3. Density of liquids
4. Pressure of oil on the surface
Option “2” is correct. Manometer is an instrument that uses a column of liquid to measure pressure, commonly referred as pressure measuring instrument.
393. ‘Pyrheliometer’ is used for measuring:
1. Sun spots
2. Solar radiation
3. Air temperature
4. Temperature of plants
Option “2” is correct. Mainly there are two types of devices that are used to measure solar radiations these are: (i) Pyrheliometer (ii) Pyranometer.
394. Spherical form of raindrop is due to-
1. Density of liquid
2. Surface tension
3. Atmospheric pressure
4. Gravitational force
Option “2” is correct. The shape of a drop of rain is constrained by the surface tension, which tries to give it the shape for which the surface area is minimum for the given volume. The spherical shape has the minimum surface area. That’s why rain drops acquire spherical shape.
395. Pressure inside a soap bubble is-
1. More than atmospheric pressure
2. Less than atmospheric pressure
3. Equal to atmospheric pressure
4. Half of atmospheric pressure
Option “1” is correct. Soap bubbles are large because when soap dissolved in water its surface tension is reduced. The pressure inside a soap bubble is more than atmospheric pressure.
396. What happens if the control rods are not used in a nuclear reactor?
1. The reactor will stop working
2. Chain process would go out of bounds
3. The reactor will be slow to act
4. The reactor will continue to work as it is
Option “2” is correct. Control rod constitutes a real-time control of fission Process which is crucial for both keeping the fusion chain reaction active and preventing it from accelerating beyond control. These rods are composed of chemical elements such as boron, silver, indium and cadmium.
397. For reproducing sound, a CD (Compact Disc) audio player uses a:
Option “3” is correct. The lens used in CD player emit ultraviolet laser beams which produce sound after reflecting through the bright surface of C.D.
398. Television signals cannot be received beyond a certain distance because:
1. Signals are weak
2. Antenna is weak
3. Air absorbs signals
4. The surface of the earth is curved
Option “4” is correct. Television signals cannot be received beyond a certain distance because the surface of the earth is curved, due to this the signals moves further without hitting the earth’s surface.
399. The principle reason why it is better to have two eyes than one is that:
1. By having two eyes we can distinguish colour easily
2. By having two eyes we can easily see in the dark as well in dim light
3. It gives a man a type of vision known as mosaic vision
4. It enhances distance and depth perception in us
Option “4” is correct. Human beings have stereoscopic vision (stereopsis) means having eyes at the front of their head. The two eyes are a few centimeters apart from each other. Due to this, two eyes see the same object from two slightly different angles and send two slightly different images to the brain. The brain combines these two images to build a three-dimensional picture of the object and we can judge the depth and distance of the object more accurately.
400. In an earthen pitcher, the water remains cold due to the process of-
1. Condensation
2. Evaporation
3. Sublimation
4. None of the above
Option “2” is correct. The water remains cold in an earthen pitcher because of a physical process is known as evaporation, when liquid changes to a gaseous (or vapour) state without boiling, it is known as evaporation.
