# MCQ of Units and Measurements | Chapter 2 | Physics | Class 11 | CBSE |

**MCQ of Units and Measurements Chapter 2, Physics, Class 11**

**Question 1: The units that are used for the fundamental physical quantities are called**

- System of unit
- Base units
- Derived units
- All of these

**Answer : B (Base units)**

**Question 2: Which of the following physical quantities have same unit in all three system of units?**

- Mass
- Length
- Time
- None of these

**Answer: C (Time)**

**Question 3: Which one of the following physical quantities is not a fundamental quantity?**

- Luminous intensity
- Thermodynamics temperature
**Electric current**- Work

**Answer: D (Work)**

**Question 4: Which one of the following statements is incorrect ?**

- Direct and indirect method are used for the measurement of physical quantities
- Scientific notations and the prefixes are used to simplify numerical computation
- A dimensionally correct equation need not to be a correct equation
- The SI units is based on six base units

**Answer: D (The SI units is based on six base units)**

**Question 5: Which of the following is unitless quantity?**

- Pressure gradient
- Displacement gradient
- Velocity gradient
- Force gradient

**Answer: B (Displacement gradient)**

**Question 6: The value of universal gravitational constant G = 6.67 x 10-11 Nm ^{2}kg^{-2}. The value of g in units of g^{-1} cm^{3} s^{-2}**

- 6.67 × 10
^{-8} - 6.67 × 10
^{-7} - 6.67 × 10
^{-9} - 6.67 × 10
^{-10}

**Answer: A (6.67 × 10 ^{-8})**

**Question 7: Which of the following is not unit of length ?**

- Angstrom
- Fermi
- Barn
- Parsec

**Answer: C (Barn)**

**Question 8: Which of the following is the smallest unit?**

- Millimetre
- Angstrom
- Fermi
- Metre

**Answer: C (Fermi)**

**Question 9: Which one of the following instrument is not used for the measurement of length?**

- Atomic clock
- Vernier callipers
- Screw gauge
- Spherometer

**Answer: A (Atomic clock)**

**Question 10: Light year is**

- Light emitted by the sun in one year
- Time taken by light to travel from sun to earth
- The distance travelled by light in free space in one year
- The time taken by Earth to go once around the sun

**Answer: C (The distance travelled by light in free space in one year)**

**You may also read MCQ of Physical World, MCQ of Motion in a Straight Line, MCQ of Motion in a Plane, MCQ of Laws of Motion, MCQ of Work, Energy and Power, MCQ of System of Particles and Rotational Motion, MCQ of Gravitation for better understanding of the chapters.**

**Question 11: Light year is the unit of**

- Distance
- Time
- Speed
- Intensity of light

**Answer: A (Distance)**

**Question 12: Which one of the following method is used to measure distance of of a planet or a star from the earth ?**

- Echo method
- Parallax method
- Triangulation method
- None of these

**Answer : B (Parallax method)**

**Question 13: The sun’s angular distance is measured to be 1920”. The distance of the sun from the earth is 1.496 × 10 ^{11} m. What is the diameter of the Sun?**

- 1.39 × 10
^{9}m - 1.39 × 10
^{10}m - 1.39 × 10
^{11}m - 1.39 × 10
^{12}m

**Answer: A (1.39 × 10 ^{9} m)**

**Question 14: What is the length of the arc of a circle of radius which subtends an angle π/6 at the centre ?**

- 11.7 cm
- 14.7 cm
- 16.7 cm
- 15.7 cm

**Answer: D (15.7 cm)**

**Question 15: The device used for measuring the mass of atoms and molecules is**

- Spring balance
- Torsional balance
- Mass spectrograph
- Common balance

**Answer: C (Mass spectrograph)**

**Question 16: If the error in measuring the radius of the sphere is 2% and that in measuring its mass is 3% , then the error in measuring the density of material of the sphere is**

- 5%
- 7%
- 9%
- 11%

**Answer: C (9%)**

**Question 17: Which of the following statements is incorrect ?**

- Every measurement by measuring instrument has same error
- A measurement can have more accuracy but less precision and vice versa
- Every calculated quantity that is based on measured values has some error
- The magnitude of the difference between the true value of the quantity and the individual measurement value is called the relative error of the measurement.

**Answer: D (The magnitude of the difference between the true value of the quantity and the individual measurement value is called the relative error of the measurement)**

**Question 18: Which of the following instruments has minimum least count?**

- A vernier callipers with 20 divisions on the vernier scale coinciding with 19 main scale division
- A Screw goes of pitch 1 mm and 100 divisions on the circular scale
- A spherometer of pitch 1 mm and 100 divisions on the circular scale
- An optical instrument that can measure length to within a wavelength of length

**Answer: D (An optical instrument that can measure length to within a wavelength of length)**

**Question 19 : Two resistors of resistances R _{1} = (300 ± 3) ohm and R_{2} = (500 ± 4)ohm are connected in series. The equivalent resistance of the series combination is**

- (800 ± 1) ohm
- (800 ± 7) ohm
- (200 ± 7) ohm
- (200 ± 1) ohm

**Answer : B ( ****(800 ± 7) ohm )**

**Question 20: Two resistors of resistances R1 = (100 ± 3) ohm and R2 = (200 ± 4)ohm are connected to parallel. The equivalent resistance of the parallel combination is **

- (66.7 ± 1.8) ohm
- (66.7 ± 4.0) ohm
- (66.7 ± 3.0) ohm
- (66.7 ± 7.0) ohm

**Answer : A ( ****(66.7 ± 1.8) ohm)**

**Question 21: The period of oscillation of a simple pendulum is T = 2π √L / g . Measured value of L is 10 cm known to 1 mm accuracy and time for 100 oscillation of the pendulum is found to be 50 s using a wrist watch of 1 s revolution. What is accuracy in the determination of g ?**

- 2 %
- 3 %
- 4 %
- 5 %

**Answer : D (5 %)**

**Question 22: A physical quantity X is related to four measurable quantities a, b, c and d as given, X = a ^{2}b^{3}c^{5/2}d^{-2} . The percentage error in the measurement of a,b,c and d are 1%, 2%, 3% and 4% respectively. What is the percentage error in quantity X?**

- 15 %
- 17 %
- 21 %
- 23 %

**Answer : C ( 21 %)**

**Question 23: Which of the following statements is incorrect regarding significant figures?**

- All the non zero digits are significant.
- All the zeros between two non zero digits are significant
- Greater the number of significant figures in a measurement, smaller is the percentage error
- The power of 10 is counted while counting the number of significant figures

**Answer: D ( The power of 10 is counted while counting the number of significant figures )**

**Question 24: Which of the following physical quantities has a unit but no dimensions?**

- Relative velocity
- Relative density
- Strain
- Angle

**Answer: D (Angle)**

**Question 25: Which of the following physical quantities has neither units nor dimensions?**

- Relative velocity
- Relative density
- Angle
- Energy

**Answer: B (Relative density)**

**Question 26: A dimensionless quantity **

- Never has a unit
- Always has unit
- May have a unit
- Does not exist

**Answer: C (May have a unit)**

**Question 27: Which of the following pairs of physical quantities have same dimensions?**

- Force and power
- Torque and energy
- Torque and power
- Force and torque

**Answer: B (Torque and energy)**

**Question 28: Which of the following sets have different dimensions?**

- Pressure, Young’s modulus , stress
- EMF , potential difference, electric potential
- Heat, work done, energy
- Dipole moment, electric flux, electric field

**Answer: D (Dipole moment, electric flux, electric field)**

**Question 29: The dimensions of planck’s constant are the same as that of**

- Linear impulse
- Work
- Linear momentum
- Angular momentum

**Answer: D (Angular momentum)**

**Question 30: dimensional formula of ∆Q, heat supplied to the system is**

- [ML
^{2}T^{-2}] - [MLT
^{-2}] - [ML
^{2}T^{-1}] - [MLT]

**Answer: A ( [ML ^{2}T^{-2}] )**

**Question 31: The dimensional formula of a physical quantity is [M ^{a}L^{b}T^{c}] . Then that physical quantity is**

- Surface tension if a =1, b=1, c=-2
- Force if a=1, b=1, c=2
- Angular frequency if a=0, b=0, c=-1
- Spring constant if a=1, b=-1 , c=-2

**Answer: C ( Angular frequency if a=0, b=0, c=-1 )**

**Question 32: Checking the correctness of equations using the method of dimensions is based on**

- The type of system
- Equality of inertial frames of references
- Principle of homogeneity of dimensions
- None of these

**Answer: C (Principle of homogeneity of dimensions)**

**Question 33: A new system of units is proposed in which unit of mass is α kg, unit of length is β m and unit of time is ϒ s. What will be value of 5 J in this system?**

- 5 α β
^{2}γ^{-2} - 5 α
^{-1}β^{-2}γ^{2} - 5 α
^{-2}β^{-1}γ^{-2} - 5 α
^{-1}β^{2}γ^{2}

**Answer: B (5 α ^{-1} β^{-2} γ^{2})**

**Question 34: If the energy, E= G ^{p} h^{q} c^{r}, where G is the universal gravitational constant, h is the planck’s constant and c is the velocity of light, then the values of p, q and r are, respectively **

- -1/2, 1/2 and 5/2
- 1/2, -1/2 and -5/2
- -1/2, 1/2 and 3/2
- 1/2, -1/2 and -3/2

**Answer: A ( ****-1/2, 1/2 and 5/2 )**

**Question 35: The equation of state of a gas is given by ( P+ a / V ^{3}) (V -b^{2}) = cT, where P,V,T are pressure, volume and temperature respectively and a,b,c are constants. The dimensions of a and b are respectively. **

- [ML
^{8}T^{-2}] and [L^{3/2}] - [ML
^{5}T^{-2}] and [L^{3}] - [ML
^{5}T^{-2}] and [L^{6}] - [ML
^{6}T^{-2}] and [L^{3/2}]

**Answer: A (** **[ML ^{8}T^{-2}] and [L^{3/2}] )**

**Question 36: The velocity of a particle (v) at an instant t is given by v = at + bt ^{2} . The dimension of b is **

- [L]
- [LT
^{-1}] - [LT
^{-2}] - [LT
^{-3}]

**Answer: D (** **[LT ^{-3}] )**

**Question 37: The time period of oscillation of a body is given by T= 2π √mgA / K ; K represents the kinetic energy, m mass, g acceleration due to gravity and A is unknown. If [A]= M ^{x}L^{y}T^{z}; then what is the value of x + y + z?**

- 3
- 2
- 1
- 5

**Answer: A (3)**

**Question 38: A potential difference V = 100 ± 5 V, when applied across a resistance, gives a current I = 10 ± 0.2 A. What is the percentage error in R?**

- 2 %
- 5 %
- 7 %
- 8 %

**Answer: C (7 %)**

**Question 39: In an experiment , the percentage of error occurred in the measurement of physical quantities A, B , C and D are 1 %, 2 %, 3 % and 4% respectively. Then the maximum percentage of error in the measurement X, where X = A ^{2} B^{1/2} / C ^{1/3} D^{3}, will be **

- 10 %
- 3 / 13 %
- 16 %
- -10 %

**Answer: C (16 %)**

**Question 40: Dimensional formula for energy in terms of momentum (p), area (A) and time (T) is **

- ρ
^{2}A^{2}T^{-1} - ρ
^{1}A^{1/2}T^{-1} - ρ
^{1/2}A^{1}T^{-1} - ρ
^{0}A^{-2}T^{-2}

**Answer: B (ρ ^{1}A^{1/2}T^{-1} )**

**Question 41: Suppose a quantity y can be dimensionally represented in terms of M, L and T, that is [y] = [M ^{a}L^{b}T^{c}] then M**

- May be represented in terms of L, T and y if a = 0
- May be represented in terms of L, T and y if a ≠ 0
- Can always be dimensionally represented in terms of L, T and y
- Can never be dimensionally represented in terms of L, T and y

**Answer: B (** **May be represented in terms of L, T and y if a ≠ 0 )**

**Question 42: Precision of measurement depends on**

- Least count of measuring instrument
- Temperature of the surroundings
- Carefulness of observer
- All of the above

**Answer: A ( ****Least count of measuring instrument )**

**Question 43: Given F= (a/t) + bt ^{2} where F denotes force and t time. The dimensions of a and b are respectively.**

- [MLT
^{-1}] and [MLT^{-4}] - [LT
^{-1}] and [T^{-2}] - [T] and [T
^{-2}] - [LT
^{-2}] and [T^{-2}]

**Answer: A ( [MLT ^{-1}] and [MLT^{-4}] )**

**Question 44: If units of length, mass and force are chosen at fundamental units, the dimensions of time would be :**

- M
^{1/2}L^{-1/2}F^{1/2} - M
^{1/2}L^{1/2}F^{1/2} - M
^{1/2}L^{1/2}F^{-1/2} - M
^{1}L^{-1/2}F^{-1/2}

**Answer: C (M ^{1/2} L^{1/2} F^{-1/2})**

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