JEE Physics Units and Measurements MCQs Set B

Question: If the buoyant force F acting on an object depends on its volume V immersed in a liquid, the density ρ of the liquid and the acceleration due to gravity g. The correct expression for F can be

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question: The dimensionally correct expression for the resistance R among the following is [P = electric power, I = electric current, t = time, V = voltage and E = electric energy]

• a)

  

• b)

  

• c)

  

• d) R = VI

Answer:

Question: Which of the following does not have dimensions of force?

• a) Work done per unit charge
• b) Work per unit length
• c) Rate of change of momentum
• d) Weight

Answer: Work per unit length

Question:

• a) [ML^5/2T–²], [L]
• b) [MLT^–2], [L²]
• c) [L], [ML^3/2 T^–2]
• d) All of these

Answer: [ML^5/2T–²], [L]

Question:

• a) [T^–2] 
• b) [T^–1]
• c) [T²]
• d) [T]

Answer: [T^–2]

Question: The dimensions of potential energy of an object in mass, length and time are respectively

• a) 1, 2, – 2
• b) –2, 1, 2
• c) 1, – 1, 2
• d) 2, 2, 1

Answer: 1, 2, – 2

Question: Which of the following is a dimensional constant?

• a) Gravitational constant
• b) Relative error
• c) Relative density
• d) Magnification

Answer: Gravitational constant

Question: The dimensions of solar constant (energy falling on earth per second per unit area) are

• a) [M T^–3]
• b) ML²T^–2]
• c) [MLT^–2]
• d) None of this

Answer: [M T^–3]

Question:

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question: The focal power of a lens has the dimensions

• a) [L^–1]
• b) [MLT^–3]
• c) [ML²T^–3]
• d) [L]

Answer: [L^–1]

Question: The exchange particles responsible for weak interactions are

• a) W and Z bosons
• b) Photons
• c) Gluons
• d) None of this

Answer: W and Z bosons

Question: Maxwell unified

• a) Electromagnetism with optics
• b) Electricity with gravitation
• c) Electricity with magnetism
• d) Electromagnetism with weak interaction

Answer: Electromagnetism with optics

Question: Which of the following is not a derived force?

• a) Electrostatic force between proton-proton
• b) van der Waal forces
• c) Tension in a string
• d) Nuclear force between proton-proton

Answer: Electrostatic force between proton-proton

Question: Which one of the following does not experience strong nuclear force?

• a) Leptons
• b) Baryons
• c) Hadrons
• d) Proton

Answer: Leptons

Question: Which of the following practical units of length is not correct?

• a) 1 light year = 9.46 × 10¹² m
• b) 1 astronomical unit = 1.496 × 10¹¹ m
• c) 1 fermi = 10^–15 m
• d) 1 parsec = 3.26 light year

Answer: 1 light year = 9.46 × 10¹² m

Question: The damping force on an oscillator is directly proportional to the velocity. The units of the constant of proportionality are

• a) kgs^–1
• b) kgs
• c) kgms^–1
• d) kgms^–2

Answer: kgs^–1

Question:

• a) [LT^–1]
• b) None of this
• c) [L^–1T]
• d) [L^1/2T^–1/2]

Answer: [LT^–1]

Question: The density of a material in CGS system of units is 4 g/cm³. In a system of units in which unit of length is 10 cm and unit of mass is 100 g, the value of density of material will be

• a) 40
• b) 400
• c) 0.4
• d) 0.04

Answer: 40

Question: What is the dimension of surface tension?

• a) [M¹L⁰T^–2]
• b) [M¹L¹T^–2]
• c) [ML¹T^–1]
• d) None of this 

Answer: [M¹L⁰T^–2]

Question:  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

• a) (a) & (d)
• b) (c) & (e)
• c) (b) & (d)
• d) (a) & (e)

Answer: (a) & (d)

Question: Which of the following has the dimensions of pressure?

• a) [ML^–1T^–2]
• b) [ML^–2T^–2]
• c) [ML^–2T^–3]
• d) None of this

Answer: [ML^–1T^–2]

Question: The dimensions of RC is

• a) Time
• b) Inverse time
• c) Square of inverse time
• d) Square of time

Answer: Time

Question: The dimensions of impulse are equal to that of

• a) Linear momentum
• b) Pressure
• c) Force
• d) Angular momentum

Answer: Linear momentum

Question:

• a) [ML⁵ T^–2]
• b) None of this
• c) [M^–1 L⁵T²]
• d) [ML⁵ T¹]

Answer: [ML⁵ T^–2]

Question: Which of the following dimensions will be the same as that of time?

• a)

  

• b)

  

• c)

  

• d) LC

Answer:

Question: Which pair do not have equal dimensions?

• a) Force and impulse
• b) Elastic modulus and pressure
• c) Angular momentum and Planck’s constant
• d) Energy and torque

Answer: Force and impulse

Question: The dimensions of Planck’s constant equals to that of

• a) Angular momentum
• b) Power
• c) Momentum
• d) Energy

Answer: Angular momentum

Question: The dimensions of universal gravitational constant are

• a) [M^–1L³T^–2]
• b) [ML²T^–1]
• c) [M^–2L³T^–2]
• d) All of these

Answer: [M^–1L³T^–2]

Question: The ratio of the dimensions of Planck’s constant and that of moment of inertia is the dimension of

• a) Frequency
• b) Time
• c) Angular momentum
• d) Velocity

Answer: Frequency

Question:

• a) LT^–2, L and T
• b) L, LT and LT^–2
• c) L², T and LT²
• d) LT², LT and L

Answer: LT^–2, L and T

Question: In a new system of units energy (E), density (d) and power (P) are taken as fundamental units, then the dimensional formula of universal gravitational constant G will be

• a) [E^–2d^–1P²]
• b) [E^–1d^–2P²]
• c) [E²d^–1P^–1
• d) [E¹d^–2P^–2]

Answer: [E^–2d^–1P²]

Question: In a practical unit if the unit of mass becomes double and that of unit of time becomes half, then 8 joule will be equal to ............. unit of work

• a) 1
• b) 10
• c) 4
• d) 6

Answer: 1

Question: The unit of “impulse per unit area” is same as that of

• a) Viscosity
• b) Surface tension
• c) Bulk modulus
• d) Force

Answer: Viscosity

Question: Even if a physical quantity depends upon three quantities, out of which two are dimensionally same, then the formula cannot be derived by the method of dimensions. This statement

• a) Must be true
• b) May be false
• c) May be true
• d) Must be false

Answer: Must be true

Question:

• a) [ML³T^–4]
• b) [ML²T^–4]
• c) [ML^–1T^–2]
• d) All of these

Answer: [ML³T^–4]

Question: The unit of length, velocity and force are doubled. Which of the following is the correct change in the other units?

• a) Unit of momentum is doubled (4
• b) Unit of time is doubled
• c) Unit of mass is doubled
• d) Unit of energy is doubled

Answer: Unit of momentum is doubled (4

Question:

• a) [ML^–1T⁰]
• b) [M²L^–2T^–4]
• c) [M²L^–2T^–2]
• d) None of these

Answer: [ML^–1T⁰]

Question:

• a) ML^–1T^–2
• b) ML²T^–1
• c) ML²T^–2
• d) MLT^–1

Answer: ML^–1T^–2

Question:  Dimensions of resistance in an electrical circuit, in terms of dimension of mass M, of length L, of time T and of current I, would be

• a) [ML²T^–3I^–2]
• b) [ML²T^–3I^–1]
• c) [ML²T^–1I^–1]
• d) All of these

Answer: [ML²T^–3I^–2]

Question: If the dimensions of a physical quantity are given by M^aL^bT^c, then the physical quantity will be

• a) Pressure if a = 1, b = –1, c = –2
• b) Acceleration if a = 1, b = 1, c = –2
• c) Velocity if a = 1, b = 0, c = –1
• d) Force if a = 0, b = –1, c = –2

Answer: Pressure if a = 1, b = –1, c = –2