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Physical Quantities and Measurement MCQs — Physics (page 5)

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.

101. 2.346 rounded to three significant figures is:

  1. 2.3
  2. 2.350
  3. 2.35
  4. 2.34

Answer: C) 2.35

Explanation: The 4th digit (6) rounds the 4 up. SLO P-11-A-07 · Understanding

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102. The SI base units of the coefficient of viscosity eta are:

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

Answer: A) kg,m^-1,s^-1

Explanation: From F = 6pieta r v: eta = F/(rv) = kg m s^-2/(m × m s^-1) = kg m^-1 s^-1. SLO P-11-A-02 · Understanding

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103. A screw gauge has pitch 0.5 mm and 50 circular divisions. Its least count is:

  1. 0.01 mm
  2. 0.1 mm
  3. 0.5 mm
  4. 0.001 mm

Answer: A) 0.01 mm

Explanation: Least count = 0.550 = 0.01 mm. SLO P-11-A-05 · Application

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104. The frequency f of a mass–spring system depends on m and spring constant ks: f = C,m^aks^b. Then

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

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

Explanation: T^-1 = M^a( MT^-2)^b: T: b = 12; M: a + b = 0 Rightarrow a = - 12: f = C ks/m. SLO P-11-A-04 · Application

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105. Which is the most reasonable estimate of the density of water?

  1. 1 kg m^-3
  2. 10,000 kg m^-3
  3. 1000 kg m^-3
  4. 100 kg m^-3

Answer: C) 1000 kg m^-3

Explanation: A sensible order of magnitude for the density of water is 1000 kg m^-3. SLO P-11-A-01 · Understanding

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106. Two masses are (4 pm 0.1) kg and (2.5 pm 0.1) kg. Their total mass is:

  1. (6.5 pm 0.1) kg
  2. (6.5 pm 0.01) kg
  3. (6.5 pm 0.2) kg
  4. (1.5 pm 0.2) kg

Answer: C) (6.5 pm 0.2) kg

Explanation: Absolute uncertainties add. SLO P-11-A-06 · Application

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107. Which quantity is dimensionless?

  1. strain
  2. force
  3. stress
  4. pressure

Answer: A) strain

Explanation: Strain is extension/original length: L/L. SLO P-11-A-03 · Application

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108. The percentage uncertainty in the measured quantity is 0.5%. For V = 43pi r^3 the percentage uncertainty is:

  1. 0.5%
  2. 1.5%
  3. 0.125%
  4. 0.167%

Answer: B) 1.5%

Explanation: A quantity raised to the power 3 has 3 times the percentage uncertainty: 3 0.5% = 1.5%. SLO P-11-A-06 · Application

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109. Which instrument gives the most precise measurement of a wire's diameter?

  1. micrometer screw gauge (0.01 mm)
  2. metre rule (1 mm)
  3. measuring tape (1 cm)
  4. vernier callipers (0.1 mm)

Answer: A) micrometer screw gauge (0.01 mm)

Explanation: The smallest least count gives the most precise reading. SLO P-11-A-05 · Application

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110. The joule (J) expressed in SI base units is:

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

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

Explanation: W = Fd: N × m = kg m^2 s^-2. SLO P-11-A-02 · Understanding

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111. Is the equation v = u + as dimensionally correct (homogeneous)?

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

Answer: D) No

Explanation: as has dimensions [ L^2T^-2], not [ LT^-1]. SLO P-11-A-03 · Application

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112. The absolute uncertainty in a reading tells us:

  1. the unit used
  2. the percentage error
  3. the number of readings taken
  4. the range within which the true value is likely to lie

Answer: D) the range within which the true value is likely to lie

Explanation: It has the same unit as the reading. SLO P-11-A-07 · Understanding

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113. If x = at + bt^2, where x is in metres and t in seconds, the units of b are:

  1. m s^-2
  2. m s^-1
  3. m s^2
  4. s^-2

Answer: A) m s^-2

Explanation: bt^2 must be in metres, so b = m/s^2. SLO P-11-A-04 · Application

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114. The speed of sound in a gas depends on pressure p and density rho: v = kp^arho^b. Then

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

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

Explanation: LT^-1 = ( ML^-1T^-2)^a( ML^-3)^b: T: a = 12; M: a + b = 0: v = k p/rho. SLO P-11-A-04 · Application

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115. The least count of a vernier callipers with 10 vernier divisions equal to 9 main-scale mm is:

  1. 0.9 mm
  2. 0.1 mm
  3. 0.01 mm
  4. 1 mm

Answer: B) 0.1 mm

Explanation: Least count = 1 mm - 0.9 mm = 0.1 mm. SLO P-11-A-05 · Application

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

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

Answer: C) No

Explanation: at has dimensions [ LT^-1], not [ L]. SLO P-11-A-03 · Application

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117. Which is the most reasonable estimate of the speed of a car on a motorway?

  1. 3000 m/s
  2. 3 m/s
  3. 30 m/s
  4. 300 m/s

Answer: C) 30 m/s

Explanation: A sensible order of magnitude for the speed of a car on a motorway is 30 m/s. SLO P-11-A-01 · Understanding

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118. Which is an example of a random uncertainty?

  1. a ruler with a worn end
  2. a balance that always reads 2 g high
  3. small fluctuations in readings due to air currents
  4. a stretched measuring tape

Answer: C) small fluctuations in readings due to air currents

Explanation: Random effects scatter readings both ways. SLO P-11-A-07 · Understanding

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119. The pascal (Pa) expressed in SI base units is:

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

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

Explanation: p = F/A: N m^-2 = kg m^-1 s^-2. SLO P-11-A-02 · Understanding

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120. The dimensions of acceleration are:

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

Answer: B) [ L T^-2]

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

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121. The percentage uncertainty in the measured quantity is 1.5%. For V = l^3 the percentage uncertainty is:

  1. 4.5%
  2. 3.375%
  3. 1.5%
  4. 0.5%

Answer: A) 4.5%

Explanation: A quantity raised to the power 3 has 3 times the percentage uncertainty: 3 1.5% = 4.5%. SLO P-11-A-06 · Application

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