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. This previous year Indian Forest Service (Main) Examination, 2021 question paper (2021) is useful for Other Jobs aspirants preparing for Central government recruitment. The paper was conducted by UPSC and reflects the official exam pattern, marking scheme and difficulty level seen in recent cycles. Use it for timed practice, topic-wise revision and understanding how questions are framed in the real examination. Download the free PDF on QuizCurrent to read instructions, attempt MCQs and compare your answers with the study notes provided on this page. Key syllabus areas include Angular velocity, Velocity of a point, Cross-section, Lorentz transformations, Momentum-energy four vector, Simple Harmonic Motion, Time period of vibration, Laser beam. Useful for Indian Forest Service (Main) Examination preparation. Helps understand the latest exam pattern. Useful for practice and self-assessment.

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) =
  • 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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