# Physics MCQs

Physics Objective (Multiple Choice) General Knowledge & General Science Questions & Answers for SSC-CGL, UPPSC, UPSC, NDA, CDS and UPSC Civil Services Prelims Examinations.

11.Optical Fibre technology works on which of these principles of Physics?

[A] Bernoulli’s Principle
[B] Newton’s law of Motion
[C] Total internal reflection of Light
[D] Photoelectric effect

Correct Answer: C [Total internal reflection of Light]

Notes:
Optical Fibre technology works on the principle of Total internal reflection of Light. It helps in transmitting light signals from one place to another with a negligible loss of energy, thereby enabling to carry more signals than copper cables.

12.Electron microscope works on which of the following principles?

[A] Optical interference
[B] Wave Nature of electrons
[C] Motion of charged particle in electromagnetic fields
[D] Faraday’s law of Electromagnetic induction

Correct Answer: B [Wave Nature of electrons]

Notes:
Electron microscope works on the principle of Wave Nature of electrons. Electron microscopes use an electron beam instead of visible light and an electron detector instead of our eyes. An electron beam allows us to see at very small scales because electrons can also behave as light due to its wave nature.

13.What is the range of masses involved in the study of Physics?

[A] 10-19 kg to 1038 kg
[B] 10-30 kg to 1055kg
[C] 10-30 kg to 1030kg
[D] 10-19 kg to 1055 kg

Correct Answer: B [10-30 kg to 1055kg]

Notes:
The range of masses involved in the study of Physics ranges from 10-30 kg to 1055 kg. 10-30kg is the mass of an electron and 1055 kg is the mass of known observable universe. The range of time scale involved in the study of Physics ranges from 10-22 s to 1018 s. The range of length involved in the study of Physics ranges from 10-14m to 1026 m.

14.The recoiling of gun is an example of which of the following?

[A] Law of Conservation of Angular Momentum
[B] Law of Conservation of Linear Momentum
[C] Conversion of Kinetic Energy to Potential Energy
[D] Law of Conservation of Energy

Correct Answer: B [Law of Conservation of Linear Momentum]

Notes:
The recoiling of gun is an example of Law of Conservation of Linear Momentum. When gun fires a bullet, it experiences a force in forward direction (action) , as a result the gun exerts a backward force (reaction) on the shoulder. Thus, it is in accordance with Law of Conservation of Linear Momentum which is also the Newton’s 3rd law of motion.

15.Which of the following pairs represent two scalar quantities?

[A] Mass, Acceleration
[B] Temperature, Torque
[C] Distance, Speed
[D] Gravitational Intensity, Work

Notes:
The physical quantities which have only magnitude and no direction are called as Scalar quantities. Some examples of Scalar quantities: Work, Mass, Temperature, Distance, Speed.

16.The branch of mechanics which deals with the study of motion of material objects without taking into account the factors which cause motion is called as:

[A] Statics
[B] Kinematics
[C] Dynamics
[D] None of the above

Notes:
The branch of mechanics which deals with the study of motion of material objects without taking into account the factors which cause motion is called as Kinematics. The branch of mechanics which deals with the study of motion of material objects taking into account the factors which cause motion is called as Dynamics. The branch of mechanics which deals with the study of material objects at rest is called as Statics.

17.What happens to the velocity of a heavy body when it undergoes an elastic collision in one dimension with a very light body at rest?

[A] it stops and comes to rest
[B] it keeps on moving with the same velocity
[C] it starts moving with half of its initial velocity
[D] it rebounds with the same velocity

Correct Answer: B [it keeps on moving with the same velocity]

Notes:
The heavy body keeps on moving with the same velocity when it undergoes an elastic collision in one dimension with a very light body at rest. Note: the body at rest starts moving with double the initial velocity of the heavy body.

18.What is the value of acceleration due to gravity at the centre of the earth?

[A] 1 N/kg
[B] 0
[C] -9.8 N/kg
[D] 9.8 N/kg

Notes:
The value of acceleration due to gravity at the centre of the earth is 0. g1 = g2(1 – d/R) As d = R in case of centre of earth, g1 = 0

19.In which of the following situations, the state of weightlessness can be observed?

[A] When objects fall freely under gravity
[B] When a satellite revolves in its orbit around the earth
[C] When bodies are at null points in outer space
[D] All of the above

Correct Answer: D [All of the above]

Notes:
The weight of a body is the force with which it is attracted towards the centre of earth. Weightlessness is a situation when the observed weight of the body becomes zero. Some of the situations of state of weightlessness are: 1. When objects fall freely under gravity 2. When a satellite revolves in its orbit around the earth 3. When bodies are at null points in outer space

20.What is the value of escape velocity for earth?

[A] 9.8 km s-2
[B] 1.6 km s-2
[C] 11.2 km s-2
[D] 7.92 km s-2