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JEE • PHYSICS • UNITS & MEASUREMENTS

Units & measurements practice · Medium

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These sets use single-correct-answer MCQs. They do not cover every JEE Main or JEE Advanced question format and are not full-length mock papers.

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331 Medium
331 of 502
Application +4 | -1
A public park, in the form of a square, has an area of (100±0.2)m2\left( {100 \pm 0.2} \right){\mathrm{m}^2} . The side of park is
View answer and explanation
Correct option: A
(10±0.01)m\left( {10 \pm 0.01} \right)m
Option A ((10±0.01)m\left( {10 \pm 0.01} \right)m) is correct because it accurately calculates the side length and its associated uncertainty using error propagation.
332 Medium
332 of 502
Application +4 | -1
The velocity of water waves (v) may depend on their
wavelength l, the density of water r and the acceleration
due to gravity, g. The method of dimensions gives the
relation between these quantities is
View answer and explanation
Correct option: B
V2∝gλ{V^2} \propto g\lambda
Option B (V2∝gλ{V^2} \propto g\lambda) is correct because dimensional analysis shows that the velocity of water waves is proportional to the square root of the product of gravity and wavelength.
333 Medium
333 of 502
Analyzing +4 | -1
The units of length, velocity and force are doubled. Which of the following is the correct change in the other units?
View answer and explanation
Correct option: C
Unit of momentum is doubled
Option C (Unit of momentum is doubled) is correct because momentum is mass times velocity, and only velocity is doubled while mass remains unchanged.
334 Medium
334 of 502
Analyzing +4 | -1
Out of the following which pair of quantities do not have same dimensions
View answer and explanation
Correct option: D
Torque and moment of inertia
Option D (Torque and moment of inertia) is correct because torque has dimensions of [ML2T−2][ML^2T^{-2}] while moment of inertia has dimensions of [ML2][ML^2].
335 Medium
335 of 502
Understanding +4 | -1
Assertion: The measure of a physical quantity is independent of the system of units.

Reason: The smaller is unit, bigger is the measure of the physical quantity and vice-versa.
View answer and explanation
Correct option: A
If both assertion and reason are true and reason is the correct explanation of the assertion.
Option A (If both assertion and reason are true and reason is the correct explanation of the assertion) is correct because the measure of a physical quantity is indeed independent of the system of units, and the reason correctly explains why.
336 Medium
336 of 502
Understanding +4 | -1
Linear momentum and angular momentum have the same dimensions in
View answer and explanation
Correct option: C
Mass and time
Option D (Mass, length and time) is correct because linear momentum has dimensions of [MLT⁻¹] and angular momentum has dimensions of [ML²T⁻¹], so they share dimensions in mass, length, and time.
337 Medium
337 of 502
Analyzing +4 | -1
The thrust developed by a rocket-motor is given by F=mv+A(p1−p2)F = mv + A\left( {{p_1} - {p_2}} \right), where m is the mass of the gas ejected per unit time, vv is velocity of the gas, A is area of cross-section of the nozzle, p1.p2{p_1}.{p_2} are the pressures of the exhaust gas and surrounding atmosphere. The formula is dimensionally
View answer and explanation
Correct option: A
Correct
Option A (Correct) is correct because each term in the equation has the dimensions of force (MLT-2), making the equation dimensionally consistent.
338 Medium
338 of 502
Application +4 | -1
A bee of mass 0.000087 kg0.000087 \mathrm{~kg} sits on a flower of mass 0.0123 kg0.0123 \mathrm{~kg}. What is the total mass supported by the stem of the flower up to appropriate significant figures?
View answer and explanation
Correct option: D
0.012 kg0.012 \mathrm{~kg}
Option D (0.012 kg0.012 \mathrm{~kg}) is correct because the sum of the masses must be rounded to the least number of significant figures, which is three in this case, based on the flower's mass.
339 Medium
339 of 502
Remembering +4 | -1
Coefficient of thermal conductivity has the dimensions
View answer and explanation
Correct option: A
[MLT−3K−1]\left[ {\mathrm{ML}{\mathrm{T}^{ - 3}}{\mathrm{K}^{ - 1}}} \right]
Option A ([MLT−3K−1]\left[ {\mathrm{ML}{\mathrm{T}^{ - 3}}{\mathrm{K}^{ - 1}}} \right]) is correct because it represents the correct dimensions for the coefficient of thermal conductivity.
340 Medium
340 of 502
Understanding +4 | -1
Assertion : Units of Rydberg constant RR are mm

Reason : It follows from Bohr's formula vˉ=R(1n12−1n22)\bar{v}=R\left(\frac{1}{n_1^2}-\frac{1}{n_2^2}\right), where the symbols have their usual meaning.
View answer and explanation
Correct option: A
If both assertion and reason are true and the reason is the correct explanation of the assertion.
Option A (If both assertion and reason are true and the reason is the correct explanation of the assertion) is correct because the units of the Rydberg constant are indeed m−1m^{-1}, and this follows directly from the Bohr formula.
341 Medium
341 of 502
Understanding +4 | -1
Statement I: The value of velocity of light is 3×108 ms−13 \times 10^8 \mathrm{~ms}^{-1} and acceleration due to gravity is 10 ms−210 \mathrm{~ms}^{-2} and the mass of proton is 1.67×10−27 kg1.67 \times 10^{-27} \mathrm{~kg}.
Statement II: The value of time in such a system is 3×107 s3 \times 10^7 \mathrm{~s}.
View answer and explanation
Correct option: B
Statement I is true, Statement II is true; Statement II is not the correct explanation for Statement I
Option D is correct because both statements are true, but Statement II does not explain Statement I. Statement II is derived from Statement I using dimensional analysis.
342 Medium
342 of 502
Understanding +4 | -1
The dimensional formula of magnetic dipole moment is
View answer and explanation
Correct option: D
[L2 A]\left[\mathrm{L}^2 \mathrm{~A}\right]
Option D is correct because the dimensional formula of magnetic dipole moment is [L²A], derived from the unit Ampere-meter squared.
343 Medium
343 of 502
Remembering +4 | -1
Dimension of force is
View answer and explanation
Correct option: B
[M1 L1 T−2]\left[\mathrm{M}^1 \mathrm{~L}^1 \mathrm{~T}^{-2}\right]
Option B ([M¹ L¹ T⁻²]) is correct because force is mass times acceleration, and the dimensions of mass, length, and time are [M], [L], and [T], respectively.
344 Medium
344 of 502
Remembering +4 | -1
The difference between the true value and measured value is called
View answer and explanation
Correct option: B
Error
Option B (Error) is correct because error is defined as the difference between the true value and the measured value of a quantity.
345 Medium
345 of 502
Application +4 | -1
The density of a material in CGS system of units is 4g/cm34g/c{m^3}, In a system of units which unit of length is 10 cm and unit of mass is 100 g , the value of density of material will be
View answer and explanation
Correct option: D
40
Option D (40) is correct because the density is transformed using the conversion factors for mass and length to the new system of units.
346 Medium
346 of 502
Understanding +4 | -1
Assertion: The equation y=x+ty=x+t cannot be true, where x,yx, y are distance and tt is time.

Reason: Quantities with different dimensions cannot be added
View answer and explanation
Correct option: A
If both assertion and reason are true and reason is the correct explanation of assertion
The correct answer is A (If both assertion and reason are true and reason is the correct explanation of assertion) because dimensional homogeneity requires that only quantities with the same dimensions can be added.
347 Medium
347 of 502
Remembering +4 | -1
A sextant is a double reflecting navigation instrument. Which of the following physical quantity, it can measure?
View answer and explanation
Correct option: B
Angular distance between two visible objects
Option B (Angular distance between two visible objects) is correct because a sextant is specifically designed to measure angles, particularly the angular distance between celestial objects or between an object and the horizon.
348 Medium
348 of 502
Remembering +4 | -1
Unit of Stefan's constant is
View answer and explanation
Correct option: B
Jm−2 s−1 K−4\mathrm{Jm}^{-2} \mathrm{~s}^{-1} \mathrm{~K}^{-4}
Option B (Jm−2 s−1 K−4\mathrm{Jm}^{-2} \mathrm{~s}^{-1} \mathrm{~K}^{-4}) is correct because Stefan's constant relates the power radiated per unit area to the fourth power of the temperature.
349 Medium
349 of 502
Remembering +4 | -1
The dimensional formula for impulse is
View answer and explanation
Correct option: B
MLT−1ML{T^{ - 1}}
Option B is correct because impulse is defined as the change in momentum, which has dimensions of mass times velocity (MLT−1MLT^{-1}).
350 Medium
350 of 502
Analyzing +4 | -1
Assertion: Two students measure the length of a stick as 1.3 m1.3 \mathrm{~m} and 1.30 m1.30 \mathrm{~m}. Both the measurements are equally accurate.

Reason: The zero at the end of a number is always meaningless.
View answer and explanation
Correct option: D
If both assertion and reason are false.
Option D is correct because both the assertion and the reason are false. The measurement 1.30 m is more accurate, and zeros at the end of a number after the decimal point are significant.
351 Medium
351 of 502
Analyzing +4 | -1
The equation of state of a real gas is given by (P+aV2)(V−b)=RT,\left(P+\frac{a}{V^2}\right)(V-b)=R T, where P,VP, V and TT are pressure, volume and temperature respectively and RR is the universal gas constant. The dimensions of ab2\frac{a}{b^2} is similar to that of:
View answer and explanation
Correct option: A
PP
Option A (PP) is correct because dimensional analysis shows that the dimensions of ab2\frac{a}{b^2} are the same as pressure.
352 Medium
352 of 502
Remembering +4 | -1
Universal time is based on
View answer and explanation
Correct option: A
Rotation of earth on its axis
Option A (Rotation of earth on its axis) is correct because universal time (UT) is defined based on the Earth's rotation.
353 Medium
353 of 502
Understanding +4 | -1
The dimensional formula for entropy is
View answer and explanation
Correct option: C
[ML2T−2K−1]\left[ {\mathrm{M}{\mathrm{L}^2}{\mathrm{T}^{ - 2}}{\mathrm{K}^{ - 1}}} \right]
Option A is correct because the fringe width in a diffraction pattern is inversely proportional to the diameter of the wire. Increasing the diameter decreases the fringe width.
354 Medium
354 of 502
Application +4 | -1
The radius of gold nucleus is 41.3 fermi. Express its volume in m3\mathrm{m}^3.
View answer and explanation
Correct option: A
2.95×10−40 m32.95 \times 10^{-40} \mathrm{~m}^3
Option A (2.95×10−40 m32.95 \times 10^{-40} \mathrm{~m}^3) is correct because it is the volume calculated using the given radius of the gold nucleus.
355 Medium
355 of 502
Understanding +4 | -1
The dimensional formula of relative density is
View answer and explanation
Correct option: D
Dimensionless
Option D (Dimensionless) is correct because relative density is the ratio of two densities, and the dimensions cancel out.
356 Medium
356 of 502
Analyzing +4 | -1
Which two of the following five physical parameters have the same dimensions?
(A) Energy density

(B) Refractive index
(C) Dielectric constant
(D) Young's modulus
(E) Magnetic field
View answer and explanation
Correct option: C
(A) and (D)
Option C ((A) and (D)) is correct because both energy density and Young's modulus have the same dimensions of ML−1T−2\mathrm{{ML}}^{-1} \mathrm{{T}}^{-2}.
357 Medium
357 of 502
Application +4 | -1
If Q denote the charge on the plate of a capacitor of
capacitance C then the dimensional formula for
Q2C\frac{{{Q^2}}}{C} is
View answer and explanation
Correct option: C
[L2MT−2]\left[ {{L^2}M{T^{ - 2}}} \right]
Option C ([L²MT⁻²]) is correct because Q²/C represents energy stored in a capacitor, which has the same dimensions as energy (ML²T⁻²).
358 Medium
358 of 502
Understanding +4 | -1
Which of the following is/are the units of strength of magnetic field at a point?
View answer and explanation
Correct option: C
NA−1  m−1\mathrm{N}{\mathrm{A}^{ - 1}}\mathrm{\;}{\mathrm{m}^{ - 1}}
Option C is correct because the unit of magnetic field strength (B) is Tesla (T), which is equivalent to N/A·m or N A⁻¹ m⁻¹.
359 Medium
359 of 502
Remembering +4 | -1
Faraday is the unit of
View answer and explanation
Correct option: A
Charge
Option A (Charge) is correct because Faraday is the unit of electric charge, representing the amount of charge carried by one mole of electrons.
360 Medium
360 of 502
Remembering +4 | -1
The difference in the lengths of a mean solar day and a side real day is about
View answer and explanation
Correct option: B
4 min
Option B (4 min) is correct because the difference between a mean solar day and a sidereal day is approximately 4 minutes.
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