Physics MCQs
Physics Objective (Multiple Choice) General Knowledge & General Science Questions & Answers for SSC-CGL, UPPSC, NDA, CDS and all one day examinations of India.
11. The centripetal force and centrifugal force are ______:
[A] equal in magnitude and have same direction
[B] unequal in magnitude and have same direction
[C] equal in magnitude and have opposite direction
[D] unequal in magnitude and have opposite direction
Show Answer
Correct Answer: C [equal in magnitude and have opposite direction]
Notes:
The centripetal force and centrifugal force are equal in magnitude and have opposite direction. Centrifugal force can be regarded as the reaction of centripetal force.
12. Which of the following is NOT correct about the velocity of rocket at any time?
[A] it is directly proportional to the exhaust speed of the gases
[B] it is directly proportional to the natural log of ratio of intial mass of rocket to its mass at that instant
[C] length of the rocket
[D] All of the above
Show Answer
Correct Answer: C [length of the rocket]
Notes:
The velocity of rocket at any time is directly proportional to the exhaust speed of the gases and to the natural log of ratio of intial mass of rocket to its mass at that instant. V = u log(m1/m2)
13. The thrust on the rocket is:
[A] in the same direction of the rocket
[B] in the opposite direction of the rocket
[C] at 90° to the direction of the rocket
[D] None of the above
Show Answer
Correct Answer: B [in the opposite direction of the rocket]
Notes:
The thrust on the rocket is in the opposite direction of the rocket. The thrust is the force with which rocket moves upwards. F = -u (dm/dt)
14. Which of the following is NOT a conservative force?
[A] Electrostatic force
[B] Magnetic force
[C] Force in an elastic spring
[D] Frictional force
Show Answer
Correct Answer: D [Frictional force]
Notes:
A conservative force is a force with the property that the work done in moving a particle between two points is independent of the taken path. Examples: Electrostatic force, Magnetic force, Force in an elastic spring Frictional force is a non-conservative force.
15. What will be the work done in holding a 25 kg iron plate for 25 seconds?
[A] 25 j
[B] 1 j
[C] 0
[D] 625 j
Show Answer
Correct Answer: C [0]
Notes:
The work done in holding a 25 kg iron plate for 25 seconds will be zero as there is no displacement taking place. Work done = Force x Displacement
16. Which is correct about the height of a capillary column of a liquid, at a particular temperature, as per Jurin’s law?
[A] equal to the diameter of the tube
[B] directly proportional to the diameter of the tube
[C] inversely proportional to the diameter of the tube
[D] half of the diameter of the tube
Show Answer
Correct Answer: C [inversely proportional to the diameter of the tube]
Notes:
Jurin’s law: the height of a capillary column of a liquid at a particular temperature is inversely proportional to the diameter of the tube.
17. Which of the following conditions will not show any Doppler effect?
[A] When source and listener both are at rest
[B] When medium alone is moving
[C] When source and listener are moving in mutually perpendicular directions
[D] All of the above
Show Answer
Correct Answer: D [All of the above]
Notes:
Conditions for no Doppler effect : (i) When source (S) and listener (L) both are at rest. (ii) When medium alone is moving. (iii) When S and L move in such a way that distance between S and L remains constant. (iv) When source S and listener L, are moving in mutually perpendicular directions
18. Which of the following is correct about a Sound wave?
[A] It is a mechanical wave
[B] It is an electromagnetic wave
[C] It is both a mechanical and electromagnetic wave
[D] It is neither a mechanical nor an electromagnetic wave
Show Answer
Correct Answer: A [It is a mechanical wave]
Notes:
Sound is a mechanical wave and cannot travel through a vacuum. It needs a medium to travel.
19. What is the S.I unit of heat energy?
[A] Joule
[B] Kelvin
[C] Candela
[D] Ampere
Show Answer
Correct Answer: A [Joule]
Notes:
The SI unit of heat energy transferred is expressed in joule (J) while SI unit of temperature is Kelvin (K), and degree Celsius (°C) is a commonly used unit of temperature.
20. Which of the following is the mirror formula?
[A] v + u =f
[B] 1/v + 1/u = 1/f
[C] 1/v + 1/u = f
[D] None of the above
Show Answer
Correct Answer: B [1/v + 1/u = 1/f]
Notes:
Mirror formula represents image distance (v), object distance (u) and focal length (f) of the mirror. The mirror formula is 1/v + 1/u = 1/f. In case of lens it is 1/v – 1/u = 1/f.
