211. When a piece of ice floating in a glass of water melts, the level of water will:
1. Fall
2. Rise
3. Remain same
4. Fall or rise depends on the temperature of water
Option “3” is correct. We know that the mass of liquid displaced by the floating ice equals to the mass of the object. That’s why the ice caps float on water. Similarly, when an ice cube melts in a glass of water, the water level does not change as the melted water will occupy exactly the same amount of space as the ice under the water level previously occupied.
212. Satellite is kept moving in its orbit around the Earth; it is due to-
1. Centrifugal force
2. Centripetal force
3. Gravitational force or lack of it
4. Some other forces
Option “2” is correct. Centripetal force is a real force that counteracts the centrifugal force and prevents the object from “flying out,” keeping it moving instead with a uniform speed along a circular path.
Option “4” is correct. The escape velocity of earth is 11.2 km/sec.
214. Which one of the following colours is seen in the middle of a Rainbow?
1. Blue
2. Green
3. Red
4. Yellow
Option “2” is correct. The correct order of colors of the rainbow is Red, Orange, Yellow, Green, Blue, Indigo and Violet. Thus it is clear that ‘Green’ Color is seen in the middle of Rainbow (VIBGYOR).
215. In which direction the rainbow is seen at 12 noon?
1. In the West
2. In the South
3. In the East
4. It cannot be seen
Option “4” is correct. A rainbow is located opposite to the sun; this explains why rainbow is not seen at 12 noon with the sun overhead.
216. Colour in a colour television is produced by a combination of three basic colours, they are:-
1. Red, blue and orange
2. Red, green and blue
3. Red, yellow and green
4. Red, green and brown
Option “2” is correct. The cathode ray tube (CRT), which is used in colour television uses three different phosphors which emit red, green and blue light respectively. They are packed together in stripes or clusters called “triads”.
Option “2” is correct. An anemometer is a device for measuring wind speed .
218.Match the correct: 1. a
2. b
3. c
4. d
Option “2” is correct. Fathometer is an instrument used to determine the depth of water or a submerged object by means of ultrasound waves. The barometer is used to measure atmospheric pressure, Hygrometer is used to measure atmospheric moisture and Altimeter is used to measure altitude/height of an object above a fixed level.
219. Force is the product of-
1. Mass and velocity
2. Mass and acceleration
3. Weight and velocity
4. Weight and acceleration
Option “2” is correct. Force = Mass × Acceleration = m.a.
220. A radio station broadcast at 30 metre band. The frequency of the carrier wave transmitted by this station is:-
1. a
