UPSC General Science: Light and Mechanics-2

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Today’s Topic: Light and Mechanics-2

  1. Assertion (A) : In a motion picture, usually 24 frames are projected every second over the whole length of the film.

Reason(R) : An image form on the retina of eyes persist for about 0.1 after the removal stimulus.

a) Both A and R are true but R is not correct explanation of A.

b) A is true but R is false.

c) Both A and R are true but R is the correct explanation of A.

d) A is false but R is true.

Ans:     B

Explanation:    In a motion picture 24 frames are projected in a second to create the illusion of continuity. The visual sensation of a particular object for about 1/16s after changes. So A true but R false.

2. When a particle moved from A to B and the distance between these is 20 m after he reached at B he returns to A. What are the displacement and distance traveled by that particle?

a) Distance is 40m and displacement 20 m                             b) Distance is 40 m and displacement 0 m

c) Displacement and distance both zero                                  d) Distance zero but displacement 40 m

Ans      B

Explanation:    The shortest distance between two points is called displacement and when any particle moved from one to another point distance never be zero.

3. An oil tanker is partially filled with oil and moves forward on the level of road with uniform acceleration. The free surface of oil then:

a) Assumed parabolic curve

b) Remain horizontal

c) Is inclined to the horizontal with large depth at the rear end

d) None of these

Ans:     C

Explanation:    An oil tanker is partially filled with oil and moves forward on the level of road with uniform acceleration. Then free space/surface of oil is inclined to the horizontal with larger depth at the rear end. So option (c) is correct.

4. Consider the following statements:

An ordinary light bulb has rather short life because the:

1) Bulb cannot be evacuated completely

2) Filament wire is not uniform

3) Wire is supporting filament melt at high temperatures

Which of the following statements are correct

a) 1, 2 and                           3 b) 1 and 2                           c) 2 and 3                    d) 1 and 3

Ans:    C

Explanation:    The ordinary bulb the filament is not uniform and the glass chamber is not evacuated completely. So due to process of gases, at high temperature, the supporting filament melt at high temperature.

5. Assertion (A) : Information is fast becoming very important field of actively in India.

Reason(R) : Software is one of the major exports of the country and India has very strong base in hard ware.


a) A is true but R false

b) R is true but A false

c) Both A and R are true but R is the correct explanation A.

d) Both A and R are true and R is the not correct information /explanation of A.

Ans:     A

Explanation:    It is correct that information technology is fast becoming a very important field activity in India. It is also true that software is one of the major export in India but India does not have a strong base in hardware.

6. Consider the following statements: Glass can be etched or scratched by:

1) Carbonic acid          2) Diamond                 3) Aquaregia                4) Hydrofluoric acid

Which of these statements are correct?

a) 1 and 4                           b) 2 and 4                           c) 3 and 4                    d) 1, 2, 3 and 4

Ans:     B

Explanation:    The hardest elements diamond is used to cut or scratched the glass. Writing on the glass with the help of hydrofluoric acid.

7. Which of the following is/are present in the largest amount in terms of percent by mass in the earth crust:

a) Oxygen                           b) Oxygen and Calcium                           c) Silicon                     d) Carbon

Ans:     C

Explanation:    Silicon is presented in the largest in terms of percentage by mass on earth. The lithosphere is called siol and sima due to the major presence of silicon.

8. Which of the following elements is/are paramagnetic in nature:

a) Iron and Nitrogen                                   b) Oxygen and Hydrogen

c) Nitrogen and Hydrogen                           d) Only Oxygen.

Ans:     D

Explanation:    Oxygen is paramagnetic in nature. In these substances, each atom has a permanent magnetic moment and it behaves like a magnetic dipole or a tiny atomic magnet which is called the atomic magnets.

9. A simple machine helps a person is doing:

a) The same amount of work much faster                           b) The same amount of work slowly

c) Less work                                                                         d) The same amount of work with lesser force

Ans:     D

Explanation:    Simple machine help us in doing same amount of work with lesser force. Simple machine has multiples force. Force apply for force at a convenient direction and points. But a machine does not work itself when energy is supplied to it, it does useful work.

10. The velocity changing with respect to time is called:

a) Displacement                           b) Speed                           c) Force                 d) Acceleration

Ans:     D

Explanation:    The velocity changing with respect to time is known as acceleration. It is calculated by a = V – u/t where V is final velocity and u is initial velocity and t is time.