Important Questions of Units and Measurement Class 11 Physics
Summary
The most important questions from Units and Measurement Class 11 Physics cover SI units and their definitions, dimensional analysis, conversion of units, significant figures, errors in measurement, and NCERT-based numericals on distances like the size of the moon and quasars. These topics carry 2–5 marks in CBSE board exams and form the foundation of JEE Main Physics Paper 1.
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Get important questions of Units and Measurement Class 11 Physics exams. View 11th Physics other chapters' important questions from an exam point of view. These important questions will play a significant role in clearing concepts of the subject. This question bank is designed by top IITian Faculties keeping NCERT in mind, and the questions are updated with respect to upcoming Board exams.
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You will get here all the important questions with answers for the class 11 Physics Chapter Units and Measurement. Click Here for Detailed Notes of Units and Measurements along with any chapter. [esquestion] What is a unit? Give an example. #sol# [/esquestion] [esquestion] What is the necessity of selecting some units as fundamental units? #sol# [/esquestion] [esquestion] Define the S.I. unit of solid angle. #sol# [/esquestion] [esquestion] Define light year. #sol# [/esquestion] [esquestion] Define a parsec. #sol# [/esquestion] [esquestion] What is the largest practical unit of mass? #sol# [/esquestion] [esquestion] What is lunar month? #sol# [/esquestion] [esquestion] How many shakes are there in 1 second? #sol# [/esquestion] [esquestion] What is a leap year? #sol# [/esquestion] [esquestion] The farthest objects in our universe are known as quasars (quasi-stellar radio sources). Much is not known about these objects. Electromagnetic wave emitted by quasars take billions of years to reach earth. Calculate distance of a quasar from which electromagnetic wave take three billion years to reach earth. #tag# [NCERT] #sol# [/esquestion] [esquestion] The radius of the hydrogen atom is nearly 0.5 A.What is the total atomic volume in of a mole of hydrogen atoms? #tag# [NCERT] #sol# [/esquestion] [esquestion] The moon is observed from two diametrically opposite points and on earth. The angle subtended at the moon by the two directions of observation is ' Given the diameter of earthto be about . Calculate the distance of the moon form the earth. #tag# [NCERT] #sol# [/esquestion] [esquestion] The sun's angular diameter is measured to be 1920. The distance of the sun from the earth is What is the diameter of the sun? #tag# [NCERT] #sol# [/esquestion] [esquestion] Give examples of three physical quantities which have the same dimensions. #sol# [esquestion] What is the unit of pressure if the unit of mass is kg, the unit of length is metre and the unit of time is minute? #sol# [/esquestion] [esquestion] Convert into erg. #sol# [/esquestion] [esquestion] Calculate the value of force 100 dynes on a system based on a metre, kilogram and minute as fundamental units. #sol# [/esquestion] [esquestion] What is a vector? #sol# [/esquestion] [esquestion] What are co-initial and collinear vectors? #sol# [/esquestion] [esquestion] What is the significance of vector? #sol# [/esquestion] [esquestion] Can three unequal forces add upto zero? #sol# [/esquestion] [esquestion] Under what condition the directions of sum and difference of two vectors will be same? #sol# [/esquestion] [esquestion] Point out the essential condition for the addition of vectors. #sol#
[/esquestion] [esquestion] What is the difference between and #sol# [/esquestion] [esquestion] Which of the following quantities are independent of the choice of orientation of the co-ordinate axes? angle between and where is a scalar? #tag# [NCERT] #sol# [/esquestion] [esquestion] A vector has magnitude and direction. Does it have a location in space? Will two equal vectors and at different locations in space necessarily have identical physical effects? #tag# [NCERT] #sol# [/esquestion] [esquestion] Pick out the two scalar quantities in the following list: Force, angular momentum, work, current, linear momentum, electric field, average velocity, magnetic moment, reaction as per Newton's third law, relative velocity. #tag# [NCERT] #sol# [/esquestion] [esquestion] Pick out only the vector quantities from the following list: Temperature, pressure, impulse, time, power, total path length, energy, gravitational potential, coefficient of friction and charge. #tag# [NCERT] #sol# [/esquestion] [esquestion] Can you associate vectors with (i) length of a wire bent into a loop (ii) a plane area (iii) a sphere? #tag# [NCERT] #sol# [/esquestion] [esquestion] A vector has both magnitude and direction. Does that mean anything that has magnitude and direction is necessarily a vector? The rotation of a body can be specified by the direction of the axis of rotation and the angle of rotation about the axis. Does that make any rotation a vector? #tag# [NCERT] #sol# [/esquestion] [esquestion] The position of a particle is given by $\left.3.0 t \hat{i}+2.0 t^{2} \hat{j}+5.0 \hat{k}\right)$ #tag# [NCERT] #sol# [/esquestion]
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Frequently Asked Questions
What is the difference between accuracy and precision in measurement?
Accuracy refers to how close a measured value is to the true or accepted value. Precision refers to how consistent repeated measurements are with each other, regardless of whether they match the true value. A measurement can be precise but inaccurate (systematic error), or accurate but imprecise (random error).
Is Units and Measurement important for JEE Main?
Yes, Units and Measurement is directly tested in JEE Main every year. Questions typically involve dimensional analysis to verify or derive formulae, unit conversion between CGS and SI systems, and error analysis in measurements. According to NTA's official JEE Main question paper trends, at least 1–2 questions appear from this chapter annually.
Which topics in Units and Measurement are most important for CBSE boards?
For CBSE boards, focus on: definitions of SI units and supplementary units, significant figures, types of errors (systematic, random, gross), error propagation in addition/multiplication, and the NCERT numericals on the Moon, Sun and quasars. These topics together account for the majority of questions that appear in board papers.
How is dimensional analysis used to check a physics formula?
Write the dimensional formula for every physical quantity in the equation. Substitute these into the equation and simplify both sides. If the dimensions on the left-hand side equal those on the right-hand side, the equation is dimensionally consistent. For example, for v = u + at: [LT⁻¹] = [LT⁻¹] + [LT⁻²][T] = [LT⁻¹]. Both sides match, so the formula is dimensionally correct.
What is the difference between fundamental and derived units?
Fundamental (or base) units measure quantities that are independent of each other — there are 7 in the SI system (metre, kilogram, second, ampere, kelvin, mole, candela). Derived units are combinations of fundamental units used to measure dependent physical quantities. For example, the newton (N = kg·m·s⁻²) is derived from the fundamental units of mass, length, and time.
How do you find the number of significant figures in a measurement?
All non-zero digits are significant. Zeros between non-zero digits are significant. Leading zeros (before the first non-zero digit) are not significant. Trailing zeros after a decimal point are significant. For example: 0.00450 has 3 significant figures; 4500 has 2 significant figures (unless a decimal point is shown).
What is the difference between systematic error and random error?
Systematic error is consistent and repeatable — it occurs in the same direction every time due to faulty instruments, incorrect calibration, or a flawed measurement technique. Random error is unpredictable and varies in direction from one measurement to another, caused by small fluctuations in the environment. Systematic errors can be corrected; random errors can be reduced by taking multiple measurements and averaging.
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