Indian Forest Service Physics Paper I 2021 Question Paper PDF

Central Government Jobs Other Jobs 2021

  • Year 2021
  • Conducted By UPSC
  • Questions 8
  • Maximum Marks 200
  • Duration Three Hours
  • Languages English

Exam Details

Detail Information
Examination Indian Forest Service (Main) Examination
Year 2021
Conducting Body UPSC
Paper Physics Paper - I
Subject Physics
Duration Three Hours
Maximum Marks 200
Number of Questions 8
Question Type Mixed

This document contains the Indian Forest Service (Main) Examination, 2021, Physics Paper I. Conducted by UPSC, this paper is designed to assess candidates' in-depth knowledge of Physics. It comprises a total of 8 questions, with candidates required to attempt 5, including compulsory questions 1 and 5. The paper is allocated a maximum of 200 marks and a duration of three hours. This paper is crucial for aspirants aiming to qualify for the prestigious Indian Forest Service.

Major Topics Covered

  • Angular velocity
  • Velocity of a point
  • Cross-section
  • Lorentz transformations
  • Momentum-energy four vector
  • Simple Harmonic Motion
  • Time period of vibration
  • Laser beam
  • Photons
  • Aircraft acceleration
  • Tension in string
  • Equilibrium angle
  • Kinetic energy
  • External torque

Why This Paper is Important

  • Useful for Indian Forest Service (Main) Examination preparation
  • Helps understand the latest exam pattern
  • Useful for practice and self-assessment
  • Covers frequently asked General Studies topics
  • Helpful for analysing question trends

Related Resources

  • Indian Forest Service (Main) Examination, 2021 - General Studies Paper - I
  • Indian Forest Service (Main) Examination, 2021 - General Studies Paper - II
  • Indian Forest Service (Main) Examination, 2021 - Physics Paper - II
  • Indian Forest Service (Main) Examination, 2021 - Physics Paper - I Answer Key
  • Indian Forest Service (Main) Examination Physics Syllabus
  • UPSC Main Exam Syllabus
  • Indian Forest Service (Main) Examination Pattern
  • UPSC Exam Pattern

Instructions

  • There are EIGHT questions in all, out of which FIVE are to be attempted.
  • Out of the remaining SIX questions, THREE are to be attempted selecting at least ONE question from each of the two Sections A and B.
  • Attempts of questions shall be counted in sequential order.
  • Unless struck off, attempt of a question shall be counted even if attempted partly.
  • Any page or portion of the page left blank in the Question-cum-Answer Booklet must be clearly struck off.
  • The number of marks carried by a question/part is indicated against it.
  • Unless otherwise mentioned, symbols and notations have their usual standard meanings.
  • Assume suitable data, if necessary and indicate the same clearly.
  • Neat sketches may be drawn, wherever required.
  • Answers must be written in ENGLISH only.
  • Useful Constants: =
  • 602 \times 10^{-19} C Electron charge (e) =
  • 109 \times 10^{-31} kg Electron rest mass (m_e) =
  • 672 \times 10^{-27} kg Proton mass (m_n) =
  • 854 \times 10^{-12} farad/m Vacuum permittivity (\varepsilon_0) =
  • 257 \times 10^{-6} henry/m Vacuum permeability (\mu_0) = 3 \times 10^8 m/s Velocity of light in free space (c) =
  • 380 \times 10^{-23} J/K Boltzmann constant (k) =
  • 602 \times 10^{-19} J Electron volt (eV) =
  • 626 \times 10^{-34} J s Planck constant (h) =
  • 67 \times 10^{-8} \text{ W m}^{-2} \text{ K}^{-4} Stefan constant (\sigma) =
  • 022 \times 10^{26} kmol-1 Avogadro number (N) =
  • 31 \times 10^3 J kmol-1 K-1 Gas constant (R) exp(1) = 2.

Questions (page 2)

Section A

Q1.

(a) Define the angular velocity ω of a rigid body rotating about some axis. Then derive the relation \overrightarrowv = \overrightarrowω × \overrightarrowr for the velocity of a point in the body with position vector \overrightarrowr relative to an origin on the axis. Draw a diagram explaining all the vectors.

(b) A comet of mass m moves towards the Sun with initial velocity v0. The mass of the sun is M and its radius is R. Find the total cross-section σ for striking the Sun. Take the Sun to be at rest and ignore all other bodies.

(c) Obtain the Lorentz transformations for the components of the momentum-energy four vector.

(d) A body executes Simple Harmonic Motion such that its velocity at the mean position is 2.0 m/s and acceleration at one of the extremities is 1.57 \text m/s^2. Calculate the time period of vibration.

(e) Consider that a continuous laser beam which is assumed to be perfectly monochromatic with a wavelength of 6500 Å is chopped into 2 ns pulses using a shutter. Calculate the number of photons in each pulse, if the power of each pulse is 5 mW.

Section A

Q2.

(a) During take-off, an aircraft accelerates horizontally in a straight line at a rate A. A small bob of mass m is suspended on a string attached to the roof of the cabin, and a hydrogen balloon (total mass m) is tethered to the floor by a string. For each, determine the tension in the string and the equilibrium angle θ between string and vertical. Draw a neat diagram to explain your answer.

(b) A rigid body is rotating under the influence of an external torque (N) acting on it. If T is the kinetic energy and ω is the angular velocity, show that (dT)/(dt) = N \cdot ω in the principal axes system.

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Frequently asked questions

What is the name of the exam?

The exam is the Indian Forest Service (Main) Examination, 2021.

Which paper is this?

This is Physics Paper - I.

Who conducts the Indian Forest Service Examination?

The Union Public Service Commission (UPSC) conducts the Indian Forest Service Examination.

What is the maximum marks for Physics Paper - I?

The maximum marks for Physics Paper - I is 200.

What is the time allowed for this paper?

The time allowed for Physics Paper - I is Three Hours.

How many questions are there in total?

There are 8 questions in total.

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