West Bengal PSC Previous Year Physics Questions with Answers (Part 1)

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WBPSC (West Bengal Public Service Commission) previous year questions and answers on Physics.

In this series we have arranged the WB PSC previous year questions related to Physics on the topic wise. This post is Part 1. 

View Part-2. 

 View Part-3

View Part-4 

Actually, It is the part of WBPSC Previous Year Science Questions with Solution series.

 

Unit:

Q. What is the unit of Power?          [WBPSC Miscellaneous Exam-2012 (1st)]

  1. Half life
  2. Watt
  3. Volt
  4. Jule

B. Watt

Explanation: Unit of Potential difference is volt. Unit of Energy is Jule.

Q. What is the unit of volume in CGS system ?      [WBPSC Miscellaneous Exam-2012 (1st)]

  1. Cm2
  2. Cm3
  3. Km
  4. m

B.Cm3

Explanation: Unit of length in CGS system is Cm. So, unit of volume is 

Cm×Cm×Cm=Cm3
C=Centimetre (unit of length); G=Gram (unit of mass); S=Second (unit of time).

Q. Unit of wave length is     [WBPSC Miscellaneous Exam- 2012 (1st)]

  1. Cm
  2. Pascal
  3. Sec.
  4. Cm/sec

A.Cm

Explanation: Unit of wave length is same as unit of length.

Q. Unit of frequency is          [WBPSC Miscellaneous Exam- 2012 (2nd)]

  1. Kg-m
  2. Sec.
  3. Hertz
  4. Cm/sec2

C.Hertz

Explanation: 1 Hertz (Hz) is equal to 1 cycle per second. Second is the unit of time. Cm/sec2 is the unit of acceleration.

Q. Kilo-Watt-Hour is the unit of          [WBPSC Miscellaneous Exam- 2012 (2nd)]

  1. Power
  2. Force
  3. Energy
  4. Momentum

C.Energy

Explanation: Kilo-Watt is the unit of Power. Hour is the unit of time. 

Therefore, Power×time=(Energy/time)×time=Energy

Q. 1 nm is equivalent to         [WBCS Preliminary-2017]

  1. 10Å
  2. 100Å
  3. 10µm
  4. 0.01mm

A.10Å

Explanation: 1nm (nanometre)=10-9 metre. 

1Å(angstrom)=10-10 metre.

1µm(micrometre)=10-6 metre.

1mm(millimetre)=10-3 metre.

Q. Light year is        
[WBCS Preliminary- 2019]

  1. light emitted by Sun in one year
  2. time taken by light to travel from Sun to Earth
  3. the distance traveled by light in free space in one year
  4. time taken by earth to go once around the Sun

C. the distance traveled by light in free space in one year.

Explanation: Light year is the unit of distance.

Q. Which of the following is not a unit of distance?       
[WBCS Preliminary- 2021]

  1. Light year
  2. Parsec
  3. Furlong
  4. Jiffy

D. Jiffy

Explanation:

  • Light year: It represents the distance traveled by light in one year. 
  • Parsec: It is a unit of distance used to measure large distance outside the solar system.
    1parsec≈3.26 light year 
  • Furlong: It is unit of distance.
    1Furlong=(1/8)mile 
  • Jiffy: It is a unit of time.

Physical Quantity:

Q. Which of the following is scalar quantity?         [WBPSC Miscellaneous Exam-2012 (2nd)]

  1. Momentum
  2. Mass
  3. Weight
  4. Force

B.Mass

Explanation: Scalar quantity has only magnitude (e.g. mass, work).

Vector quantity has magnitude and direction (e.g. momentum, weight, force etc.)

Environment:

Q. Which one of the following does not cause global warming?       [WBPSC Clerkship Exam-2019 (2nd)]

  1. Burning fossil fuels
  2. Petrol cars
  3. Solar  energy
  4. Deforestation

C. Solar energy

Explanation: Global warming usually refers to human induced long term heating of Earth's climate. 

Main cause: Increase of green house gas.

Q. Coal, Petroleum and Natural Gas are example of           [WBCS Preliminary- 2015]

  1. Fossil Fuels
  2. Cryogenic Fuels
  3. Indigenous Fuels
  4. Radioactive Fuels

A. Fossil Fuels

Explanation: Fossil fuels include: Coal, Petroleum, natural gas etc.

  • Cryogenic Fuels require storage at extremely low temperature in order to maintain them in liquid state. These fuels are used in space.
  • Radioactive fuels are radioactive materials used in nuclear power plant.

Q. The International Day for the Preservation of the Ozone Layer is observed on                      [WBCS Preliminary- 2017]

  1. September 12
  2. September 14
  3. September 16
  4. September 20

C. September 16

Explanation: This is designated by the United Nations General Assembly on 19 December, 2000. On 16 September, 1987 nations signed the Montreal Protocol. Montreal Protocol is an international treaty designed to protect the ozone layer.

Q. On average, air contains ________ % of water vapour.          [WBCS Preliminary- 2018]

  1. 1
  2. 3
  3. 5
  4. 7

A. 1 and B. 3

Explanation: The percentage of water vapour in air varies based on temperature. It varies 0.2 percent to 4 percent.

Q. Noise pollution is created if noise is in excess to        
[WBCS Preliminary- 2019]

  1. 70-75 dB
  2. 50-60 dB
  3. 80-99 dB
  4. 40-65 dB

C. 80-99 dB

Explanation: Normal conversation is about 60 dB. In general sounds above 85 dB are harmful.

Q. Started in June, 2014 by the Union Government of India, the 'Namami Gange' Programme is associated with         
[WBCS Preliminary- 2021]

  1. Worshipping the Ganga
  2. Canal irrigation from the Ganga
  3. River linking with the Ganga
  4. National Mission for Clean Ganga

D. National Mission for clean Ganga

Explanation: 'Namami Ganga' Programme' is associated with National Mission for Clean Ganga.

Force, Work and Motion:

Q. Which of the following is not a conservative force?          [WBCS Preliminary- 2016]

  1. Gravitational force
  2. Frictional force
  3. Electrostatic force
  4. Magnetostatic force

B.Frictional force

Explanation: Total work done by the conservative force for moving a particle between tow points, only depend on displacement but independent of path taken. Hence, if a particle travels in closed loop, the total work done by conservative force is zero.

Total work done by the non-conservative force for moving a particle between two points, depends on the path taken not on the displacement.

Q. A body is acted upon by two unequal forces in opposite directions, but not in one line. The effect is that the body will have          [WBCS Preliminary- 2017]

  1. only rotational motion
  2. only translation motion
  3. neither the rotational nor the translational motion
  4. rotational as well as translational motion

D. rotational as well as translational motion

Explanation: Two forces are unequal. So, vector sum of two forces are not zero. Hence, there will be translational motion.

Two forces are unequal, acted upon opposite direction and not in one line. So, there will be rotational motion.

Q. A stone tied to a string is whirled in a circle. As it was revolving, the rope suddenly snaps. Then             [WBCS Preliminary- 2018]

  1. the stone flies off tangentially
  2. the stone moves radially outward
  3. the stone moves radially inward
  4. None of the above

A.the stone flies off tangentially

Explanation: According to the Newton's laws, if there is no force acted on a moving body, that body will continue to move in same speed with same direction.

At the time of snaps, the direction of the stone was along the tangent. Hence, the stone flies off tangentially.

Q. A bomb is dropped at a point from a moving aeroplane. The pilot observes that         
[WBCS Preliminary- 2019]

  1. the bomb traverses a curved path and falls some distance behind the point.
  2. the bomb traverses a curved path and falls some distance ahead.
  3. the bomb drops vertically downward.
  4. the bomb remains stationary in the air for some time.

B. the bomb traverses a curved path and falls some distance ahead.

Explanation: When the bomb is dropped, the bomb will have two motion, one is horizontal motion (since, the bomb was on the aeroplane) and another is vertical motion (due to gravitational force).

  • For horizontal motion the bomb will go ahead of point.
  • Since, the gravitational force perpendicular to the horizontal motion, there will be no effect of gravitational force on horizontal motion. 
  • Hence, horizontal motion and vertical motion will take place simultaneously. Eventually, the bomb traverse a curved path and falls some distance ahead.

Q. A heavy body and a light body have equal kinetic energy. Then         
[WBCS Preliminary- 2021]

  1. heavy body has greater momentum.
  2. light body has greater momentum.
  3. both have equal momentum.
  4. both have same angular momentum.

A. heavy body has greater momentum. 

Explanation:
Let, mass and velocity of heavy body are m1 and v1.
Let, mass and velocity of light body are m2 and v1.

Here, kinetic energy is equal.

Kinetic energy is equal to (1/2)*mass*velocity*velocity





m1>m2⇒v12<v22
v1<v2  .........(2)
Momentum=mass×velocity
From equation-(1), we can write,
(m1v1)×v1=(m2v2)×v2
Here, v1<v2  .....(equation-2)
⇒(m1v1)>(m2v2)
So, heavy body has greater momentum.

Q. A pendulum clock that keeps correct time on the earth, is taken to moon. It will then run          
[WBCS Preliminary- 2021]

  1. at correct rate.
  2. 6 times faster.
  3. √6 times faster.
  4. √6 times slower.

D. √6 times slower.

Explanation:
Time period of a simple pendulum is given by,

Time period of a simple pendulum is given by 2pi root under length byacceleration due to gravity
T=Time period of pendulum
l=length of the pendulum
g=acceleration due to gravity

Pendulum is the time keeping element in pendulum clock.
If time period of pendulum increases, clock will run slower.
If time period of pendulum decreases, clock will run faster.
Let, the length of the pendulum is l. So,

In moon acceleration due to gravity is (g/6).  Therefore,
Time period of simple pendulum is root 6 times of the time period of pendulum in the earth.
So, on the moon, the time period of the pendulum increases √6 times.
Therefore, on the moon, the clock will run √6 time faster.



Q. A vehicle covers half the distance with uniform speed v1 and the other half with uniform speed v2. The average speed of the vehicle is           
[WBCS Preliminary- 2021]

A. (v1+v2)/2 B. (v1+v2)/(v1v2) C.(v1v2)/(v1+v2) D.(2v1v2)/(v1+v2)
















D. (2v1v2)/(v1+v2)

Explanation:
Let, total distance be 2l.
So, time required for covering first half=(l/v1).
Time required for covering 2nd half =(l/v2).


Average speed=(Total distance/Total time)

Therefore, Average speed=

Average speed= (2v1v2)/(v1+v2)


Q. A spring constant k is cut into two equal halves. The spring constant of each half is now     
[WBCS Preliminary- 2021]

  1. k
  2. k/2
  3. 2k
  4. 4k

C. 2k

Explanation:
Spring constant k is inversely proportional to the length of the spring.

Spring constant is inversely proportional to the length of the spring.

Here, let, the length of the spring is l and spring constant is k. So,
spring constant times length is constant
Let, the spring constant be k1, if the length of the spring be (l/2). So,
From, equation (1) and (2), we can write,
So, if the spring is cut into two equal halves, the spring constant of each half is 2k.



 

 Visit Physics Part-2 of this series

Visit Physics Part-3 of this series

Visit Physics Part-4 of this series 

WBPSC Previous Year Computer Questions with Solution

WBPSC Previous Year Science Series 

 

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