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 apparent weight of the body becomes zero in which of the following cases in the elevator?
[A] during free fall of a body under gravity
[B] when elevator is accelerating downwards
[C] when elevator is at rest
[D] when elevator is accelerating upwards
Show Answer
Correct Answer: A [during free fall of a body under gravity]
Notes:
The apparent weight of the body becomes zero in an elevator during free fall of a body under gravity. It can be said that the body becomes weightless as the force of reaction between the person and the plane with which he is in contact vanishes.
12. Which of the following statements is correct?
[A] The acceleration due to gravity is same at the equator and the poles
[B] The acceleration due to gravity is maximum at the poles
[C] The acceleration due to gravity is least at the poles
[D] None of the above
Show Answer
Correct Answer: B [The acceleration due to gravity is maximum at the poles]
Notes:
The acceleration due to gravity is maximum at the poles and is least at the equator. The value of acceleration due to gravity increases as we go from the equator to the pole.
13. Which of the following is correct about the value of acceleration due to gravity?
[A] it is greater at mountains than in plains
[B] it is lesser at mountains than in plains
[C] it is equal for mountains and plains
[D] None of the above
Show Answer
Correct Answer: B [it is lesser at mountains than in plains]
Notes:
The value of acceleration due to gravity decreases with increase in height. Therefore, it is lesser at mountains than in plains.
14. If the time of revolution is T in a satellite, then kinetic energy is proportional to which of the following:
[A] T-4/3
[B] T2/3
[C] T-2/3
[D] T-1/3
Show Answer
Correct Answer: C [T-2/3]
Notes:
The square of the period of any planet is proportional to the cube of the semimajor axis of its orbit. So r is inversely proportional to cube root of the square of T. And Kinetic energy is inversely proportional to r. Therefore, K.E is directly proportional to (T)-2/3
15. What will happen if a wire of length L is cut into two or more parts?
[A] each part can hold half the weight as full length wire
[B] each part can hold the same weight as full length wire
[C] each part can hold twice the weight as full length wire
[D] None of the above
Show Answer
Correct Answer: B [each part can hold the same weight as full length wire]
Notes:
If a wire of length L is cut into two or more parts, then it’s each part can hold the same weight. Since breaking force is independent of the length of wire.
16. Which of the following is the S.I. unit of density?
[A] m-2
[B] m-3
[C] kg m-2
[D] kg m-3
Show Answer
Correct Answer: D [ kg m-3 ]
Notes:
The SI unit of density is kg m-3. It is a positive scalar quantity. The Gaussian unit of density is the gram per cubic centimeter which is equivalent to a gram per milliliter [1 g/cm3 = 1 g/ml].
17. When are the two particles said to be in same phase?
[A] if the phase difference between them is an even multiple of π
[B] if the path difference is an even multiple of (λ / 2)
[C] if the time interval is an even multiple of (T/ 2)
[D] All of the above
Show Answer
Correct Answer: D [All of the above]
Notes:
Two vibrating particle are said to be in same phase, if the phase difference between them is an even multiple of π or path difference is an even multiple of (λ / 2) or time interval is an even multiple of (T/ 2).
18. What happens to the frequency of the pendulum if it is suspended from the ceiling of the lift moving up ward with constant acceleration?
[A] it decreases
[B] it increases
[C] may increase or decrease
[D] No change
Show Answer
Correct Answer: B [it increases]
Notes:
If the lift is moving up ward with constant acceleration a then the time period of the pendulum decreases and frequency increases.
19. What is the relationship between the spring constant k and the spring length in case of spring pendulum?
[A] spring constant is inversely proportional to the spring length
[B] spring constant is directly proportional to the spring length
[C] spring constant is independent of the spring length
[D] spring constant is twice the spring length
Show Answer
Correct Answer: A [spring constant is inversely proportional to the spring length]
Notes:
The spring constant of a spring pendulum is inversely proportional to the spring length.
20. What do we call the wave if the constituents of the medium oscillate perpendicular to the direction of wave propagation?
[A] Transverse wave
[B] Longitudinal wave
[C] Electromagnetic wave
[D] Matter wave
Show Answer
Correct Answer: A [Transverse wave]
Notes:
If the constituents of the medium oscillate perpendicular to the direction of wave propagation, we call the wave a transverse wave. If they oscillate along the direction of wave propagation, we call the wave a longitudinal wave
