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Physical Quantities and Measurement MCQs — Physics (page 4)

121 multiple-choice questions on Physical Quantities and Measurement from Physics, each with the correct answer and, where available, a teacher's explanation. Read through them to revise the chapter, then practise the same questions one by one to test yourself.

76. Which is the most reasonable estimate of the diameter of an atomic nucleus?

  1. 10^-6 m
  2. 10^-10 m
  3. 10^-20 m
  4. 10^-15 m

Answer: D) 10^-15 m

Explanation: A sensible order of magnitude for the diameter of an atomic nucleus is 10^-15 m. SLO P-11-A-01 · Understanding

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77. The escape speed v depends on g and the planet's radius R: v = kg^aR^b. Then

  1. a = 12, b = - 12
  2. a = 12, b = 12
  3. a = 1, b = 1
  4. a = 2, b = 1

Answer: B) a = 12, b = 12

Explanation: LT^-1 = ( LT^-2)^a L^b: T: a = 12; L: a + b = 1 Rightarrow b = 12: v = k gR. SLO P-11-A-04 · Application

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78. Is the equation E = mc^2 dimensionally correct (homogeneous)?

  1. No
  2. Only if the constants are dimensionless
  3. Yes
  4. It cannot be checked by dimensions

Answer: C) Yes

Explanation: mc^2 has dimensions [ ML^2T^-2], the same as energy. SLO P-11-A-03 · Application

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79. Which is the most reasonable estimate of the normal walking speed of a person?

  1. 15 m/s
  2. 1.5 m/s
  3. 150 m/s
  4. 0.015 m/s

Answer: B) 1.5 m/s

Explanation: A sensible order of magnitude for the normal walking speed of a person is 1.5 m/s. SLO P-11-A-01 · Understanding

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80. Which is the most reasonable estimate of the time for one human heartbeat?

  1. 80 s
  2. 8 s
  3. 0.8 s
  4. 0.008 s

Answer: C) 0.8 s

Explanation: A sensible order of magnitude for the time for one human heartbeat is 0.8 s. SLO P-11-A-01 · Understanding

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81. Is the equation T = 2pi gl dimensionally correct (homogeneous)?

  1. It cannot be checked by dimensions
  2. Yes
  3. No
  4. Only if the constants are dimensionless

Answer: C) No

Explanation: g/l has dimensions [ T^-1], not time. SLO P-11-A-03 · Application

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82. Which is the most reasonable estimate of atmospheric pressure at sea level?

  1. 10^5 Pa
  2. 10^3 Pa
  3. 10^8 Pa
  4. 10^2 Pa

Answer: A) 10^5 Pa

Explanation: A sensible order of magnitude for atmospheric pressure at sea level is 10^5 Pa. SLO P-11-A-01 · Understanding

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83. Which is the most reasonable estimate of the temperature of the surface of the Sun?

  1. 60 K
  2. 6 10^7 K
  3. 6000 K
  4. 600 K

Answer: C) 6000 K

Explanation: A sensible order of magnitude for the temperature of the surface of the Sun is 6000 K. SLO P-11-A-01 · Understanding

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84. Timing many oscillations rather than one improves:

  1. the systematic error of the clock
  2. the value of g directly
  3. the percentage uncertainty in the period
  4. the length of the pendulum

Answer: C) the percentage uncertainty in the period

Explanation: The reaction-time uncertainty is shared over many oscillations. SLO P-11-A-05 · Application

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85. In rho = m/V, the two measured quantities have uncertainties of pm1 in 50 and pm0.5 in 10. The percentage uncertainty in the result is:

  1. 3%
  2. 2.5%
  3. 2%
  4. 7%

Answer: D) 7%

Explanation: For a product or quotient, add the percentage uncertainties: 2% + 5% = 7%. SLO P-11-A-06 · Application

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86. The dimensions of velocity are:

  1. [ L T^-1]
  2. [ M L T^-1]
  3. [ M L^2 T^-2]
  4. [ M L^-1 T^-2]

Answer: A) [ L T^-1]

Explanation: Write velocity in terms of mass, length and time: [ L T^-1]. SLO P-11-A-03 · Application

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87. Writing a result as (9.81 pm 0.05) m s^-2 means:

  1. the true value probably lies between 9.76 and 9.86 m s^-2
  2. the value is exactly 9.81
  3. the value is between 9.81 and 9.86 only
  4. the error is 5%

Answer: A) the true value probably lies between 9.76 and 9.86 m s^-2

Explanation: The range is value pm uncertainty. SLO P-11-A-07 · Understanding

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88. The volt (V) expressed in SI base units is:

  1. kg,m,s^-1
  2. kg,m^-3
  3. kg,m^2,s^-2,A^-1
  4. kg,m^2,s^-3,A^-1

Answer: D) kg,m^2,s^-3,A^-1

Explanation: V = P/I: W A^-1 = kg m^2 s^-3 A^-1. SLO P-11-A-02 · Understanding

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89. Two lengths are (102.5 pm 0.5) cm and (48 pm 0.5) cm. Their difference is:

  1. (150.5 pm 1) cm
  2. (54.5 pm 0) cm
  3. (54.5 pm 1) cm
  4. (54.5 pm 0.25) cm

Answer: C) (54.5 pm 1) cm

Explanation: For a sum or difference, add the absolute uncertainties. SLO P-11-A-06 · Application

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90. The SI base units of Young modulus are:

  1. kg,m^2,s^-2,A^-1
  2. kg,m^-3
  3. kg,m^-1,s^-2
  4. kg,m^2,s^-3

Answer: C) kg,m^-1,s^-2

Explanation: Stress/strain has the unit of stress (Pa). SLO P-11-A-02 · Understanding

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91. The SI base units of angular momentum are:

  1. kg,m^2,s^-2,A^-1
  2. kg,m^2,s^-1
  3. kg,m^2,s^-3
  4. kg,m^-1,s^-2

Answer: B) kg,m^2,s^-1

Explanation: L = mvr: kg m^2 s^-1. SLO P-11-A-02 · Understanding

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92. The dimensions of pressure are:

  1. [ M L^2 T^-1]
  2. [ M L^2 T^-3]
  3. [ M L^-1 T^-2]
  4. [ M L T^-1]

Answer: C) [ M L^-1 T^-2]

Explanation: Write pressure in terms of mass, length and time: [ M L^-1 T^-2]. SLO P-11-A-03 · Application

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93. A cylinder has r = (2.00 pm 0.02) cm and h = (10.0 pm 0.1) cm. The percentage uncertainty in its volume V = pi r^2h is:

  1. 3%
  2. 4%
  3. 2%
  4. 1%

Answer: A) 3%

Explanation: 2 1% + 1% = 3%. SLO P-11-A-06 · Application

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94. Is the equation s = ut + 12at^2 dimensionally correct (homogeneous)?

  1. Yes
  2. Only if the constants are dimensionless
  3. No
  4. It cannot be checked by dimensions

Answer: A) Yes

Explanation: Each term is a length [ L]. SLO P-11-A-03 · Application

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95. A reading is (3.2 pm 0.04). Its fractional uncertainty is:

  1. 0.04
  2. 1.25
  3. 0.0125
  4. 80

Answer: C) 0.0125

Explanation: Fractional uncertainty = 0.043.2 = 0.0125 (that is 1.25%). SLO P-11-A-06 · Application

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96. The SI base units of torque are:

  1. s^-1
  2. kg,m^2,s^-2
  3. kg,m^2,s^-3,A^-2
  4. kg,m^2,s^-3,A^-1

Answer: B) kg,m^2,s^-2

Explanation: tau = Fr: N m = kg m^2 s^-2 (same base units as energy, but a different quantity). SLO P-11-A-02 · Understanding

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97. The speed v of a wave on a string depends on tension F and mass per unit length mu: v = kF^amu^b. Then

  1. a = 2, b = 1
  2. a = - 12, b = 12
  3. a = 12, b = - 12
  4. a = 1, b = -1

Answer: C) a = 12, b = - 12

Explanation: LT^-1 = ( MLT^-2)^a( ML^-1)^b: M: a + b = 0; T: -2a = -1. So a = 12, b = - 12: v = k F/mu. SLO P-11-A-04 · Application

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98. The SI base units of density are:

  1. kg,m^-3
  2. s,A
  3. kg,m^2,s^-2,A^-1
  4. kg,m^2,s^-3

Answer: A) kg,m^-3

Explanation: Mass per unit volume. SLO P-11-A-02 · Understanding

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99. The dimensions of momentum are:

  1. [ T^-1]
  2. [ L T^-2]
  3. [ M L^2 T^-1]
  4. [ M L T^-1]

Answer: D) [ M L T^-1]

Explanation: Write momentum in terms of mass, length and time: [ M L T^-1]. SLO P-11-A-03 · Application

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100. Is the equation P = Fv dimensionally correct (homogeneous)?

  1. Only if the constants are dimensionless
  2. No
  3. It cannot be checked by dimensions
  4. Yes

Answer: D) Yes

Explanation: Force × velocity: MLT^-2 LT^-1 = ML^2T^-3, the dimensions of power. SLO P-11-A-03 · Application

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