# Physics Punjab PMS Paper I 2020

PUNJAB PUBLIC SERVICE COMMISSION

COMBINED COMPETITIVE EXAMINATION

FOR RECRUITMENT TO THE POSTS OF PROVINCIAL MANAGEMENT SERVICE-2020

SUBJECT: PHYSICS (PAPER-I)

TIME ALLOWED: THREE HOURS MAXIMUM MARKS: 100

NOTE:I. All the parts (if any) of each Question must be attempted at one place instead of at different places

II. Write Q. No. in the Answer Book in accordance with Q. No. in the Q. Paper.

III. No Page/Space be left blank between the answers. All the blank pages of Answer Book must be crossed.

IV. Extra attempt of any question or any part of the question will not be considered.

Attempt FIVE Questions in all. Attempt in Urdu or English.

Q. No. 1 (a) How can we multiply two vector quantities? Discuss in detail, the vector product, giving at least two examples. (10 Marks)

(b) Define and explain the line integral and surface integral of a vector (10 Marks)

Q. No. 2 (a) Define and derive a relation for the rotational kinetic energy of a rigid body. How will you find the rotational kinetic energy of a hoop and a solid sphere? (12 Marks)

(b) Prove that the square of time period of a planet bears a direct direct relation with the cube of the mean distance between Sun and the planet. (08 Marks)

Q. No. 3 (a) Define and briefly discuss two postulates of Special theory of relativity. (08 Marks)

(b) Discuss the consequences of Lorentz transformation for relativity of length and time. (12 Marks)

Q. No. 4 Derive Bernoulli’s equation and briefly explain its physical significance, Using this equation, establish a relation between speed and pressure of a fluid passing through a pipe of variable diameters. (20 Marks)

Q. No. 5 What is a damped harmonic oscillator? Write the equation of motion of such an oscillator and derive its solution which could help to find the displacement of damped harmonic oscillator. (20 Marks)

Q. No. 6 (a) Discuss Young’s double sit experiment in detail. How can we find the fringe width and angular spacing using this experiment? (15 Marks)

(b) Sketch a ray diagram for Michelson Interferometer. (05 Marks)

Q. No. 7 (a) What is an ideal gas? Discuss the work done on an ideal gas during thermal isolation. (10 Marks)

(b) Discuss adiabatic expansion and adiabatic compression processes. (10 Marks)

Q. No. 8 Write short note on the following: (4×5=20 Marks)

(i) Equivalence of Mass and Energy (ii) Lissajous Figures (iii) Entropy (iv) Brownian Motion