MCQs / Physics / Physical Quantities and Measurement

Physical Quantities and Measurement MCQs — Physics (page 2)

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.

26. The centripetal force on a body depends on m, v and r: F = k,m^av^br^c. Then

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

Answer: D) a = 1, b = 2, c = -1

Explanation: M: a = 1; T: -b = -2 Rightarrow b = 2; L: b + c = 1 Rightarrow c = -1: F = kmv^2/r. SLO P-11-A-04 · Application

Discuss this question

27. The SI base units of momentum are:

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

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

Explanation: p = mv. SLO P-11-A-02 · Understanding

Discuss this question

28. The result of 12.11 + 0.3 should be given as:

  1. 12.410
  2. 12.4
  3. 12
  4. 12.41

Answer: B) 12.4

Explanation: For addition, keep the least number of decimal places (1). SLO P-11-A-07 · Understanding

Discuss this question

29. The dimensions of Planck's constant h (from E = hf) are:

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

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

Explanation: h = E/f: ML^2T^-2/T^-1 = ML^2T^-1. SLO P-11-A-04 · Application

Discuss this question

30. Is the equation T = 2pi lg 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: l/g = L/ LT^-2 = T. SLO P-11-A-03 · Application

Discuss this question

31. How many significant figures are in 3.00 10^8?

  1. 1
  2. 8
  3. 9
  4. 3

Answer: D) 3

Explanation: All digits in the mantissa count. SLO P-11-A-07 · Understanding

Discuss this question

32. The SI base units of the gravitational constant G are:

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

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

Explanation: G = Fr^2/(m1 m2): N m^2 kg^-2 = kg^-1 m^3 s^-2. SLO P-11-A-02 · Understanding

Discuss this question

33. Precision of a set of measurements describes:

  1. how close the mean is to the true value
  2. the number of readings taken
  3. the size of the instrument
  4. how close the readings are to each other

Answer: D) how close the readings are to each other

Explanation: Precision is about spread (random error). SLO P-11-A-05 · Application

Discuss this question

34. The period of a pendulum is T = 2pi l/g, so g = 4pi^2l/T^2. With 1% uncertainty in l and 0.5% in T, the uncertainty in g is:

  1. 1.25%
  2. 1.5%
  3. 0.5%
  4. 2%

Answer: D) 2%

Explanation: 1% + 2 0.5% = 2%. SLO P-11-A-06 · Application

Discuss this question

35. Is the equation v^2 = u^2 + 2as dimensionally correct (homogeneous)?

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

Answer: D) Yes

Explanation: Each term has dimensions [ L^2T^-2]. SLO P-11-A-03 · Application

Discuss this question

36. The hertz (Hz) expressed in SI base units is:

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

Answer: D) s^-1

Explanation: Frequency is per second: s^-1. SLO P-11-A-02 · Understanding

Discuss this question

37. A dimensionally correct equation:

  1. must contain only base quantities
  2. can never contain constants
  3. is always physically correct
  4. may still be physically wrong (e.g. a missing numerical factor)

Answer: D) may still be physically wrong (e.g. a missing numerical factor)

Explanation: Dimensional analysis cannot detect pure numbers such as 12 or 2pi. SLO P-11-A-03 · Application

Discuss this question

38. Which is the most reasonable estimate of the thickness of a sheet of paper?

  1. 0.1 mm
  2. 1 mm
  3. 0.001 mm
  4. 1 cm

Answer: A) 0.1 mm

Explanation: A sensible order of magnitude for the thickness of a sheet of paper is 0.1 mm. SLO P-11-A-01 · Understanding

Discuss this question

39. The drag force on a small sphere depends on eta, r and v: F = keta^ar^bv^c. Then

  1. a = 2, b = 1, c = 1
  2. a = 1, b = 2, c = 1
  3. a = 1, b = 1, c = 2
  4. a = b = c = 1

Answer: D) a = b = c = 1

Explanation: MLT^-2 = ( ML^-1T^-1)^a L^b( LT^-1)^c: M: a = 1; T: -a - c = -2 Rightarrow c = 1; L: -a + b + c = 1 Rightarrow b = 1. (Stokes' law, k = 6pi.) SLO P-11-A-04 · Application

Discuss this question

40. The newton (N) expressed in SI base units is:

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

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

Explanation: F = ma: kg × m s^-2. SLO P-11-A-02 · Understanding

Discuss this question

41. Which statement is true?

  1. No measurement can be perfectly exact
  2. Uncertainty is the same as a mistake
  3. Digital meters have no uncertainty
  4. Repeating a reading removes all uncertainty

Answer: A) No measurement can be perfectly exact

Explanation: Uncertainty is always present; a mistake (blunder) is different. SLO P-11-A-07 · Understanding

Discuss this question

42. The ohm (Omega) expressed in SI base units is:

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

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

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

Discuss this question

43. Which is the most reasonable estimate of the height of a classroom door?

  1. 200 m
  2. 0.2 m
  3. 20 m
  4. 2 m

Answer: D) 2 m

Explanation: A sensible order of magnitude for the height of a classroom door is 2 m. SLO P-11-A-01 · Understanding

Discuss this question

44. A current (2.0 pm 0.1) A flows through a resistor with p.d. (8.0 pm 0.2) V. The resistance is:

  1. (4.0 pm 0.03) Omega
  2. (4.0 pm 0.5) Omega
  3. (4.0 pm 0.1) Omega
  4. (4.0 pm 0.3) Omega

Answer: D) (4.0 pm 0.3) Omega

Explanation: 5% + 2.5% = 7.5% of 4.0 Omega is 0.3 Omega. SLO P-11-A-06 · Application

Discuss this question

45. The period T of a simple pendulum depends on its length l and g: T = k,l^ag^b. Then

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

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

Explanation: T = L^a( LT^-2)^b: L: a + b = 0; T: -2b = 1. So b = - 12, a = 12, giving T = k l/g. SLO P-11-A-04 · Application

Discuss this question

46. The time t for a body to fall from height h depends on h and g: t = kh^ag^b. Then

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

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

Explanation: Same algebra as the pendulum: t = k h/g (in fact k = 2). SLO P-11-A-04 · Application

Discuss this question

47. The weber (Wb) expressed in SI base units is:

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

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

Explanation: Phi = BA: T m^2 = kg m^2 s^-2 A^-1. SLO P-11-A-02 · Understanding

Discuss this question

48. A stopwatch reads 0.2 s before it is started. All times measured with it are:

  1. more precise
  2. correct on average
  3. 0.2 s too small — a random error
  4. 0.2 s too large — a systematic error

Answer: D) 0.2 s too large — a systematic error

Explanation: Subtract the zero error from every reading. SLO P-11-A-05 · Application

Discuss this question

49. A rod's true length is 50.0 cm. Which set of readings is precise but not accurate?

  1. 50.1, 49.9, 50.0, 50.1, 49.9 cm
  2. 52.1, 52.2, 52.1, 52.0, 52.1 cm
  3. 47.0, 53.5, 49.0, 51.8, 48.6 cm
  4. 50.0 cm once only

Answer: B) 52.1, 52.2, 52.1, 52.0, 52.1 cm

Explanation: The readings agree closely (precise) but are all about 2 cm too large — a systematic error. SLO P-11-A-05 · Application

Discuss this question

50. Which is the most reasonable estimate of the diameter of an atom?

  1. 10^-10 m
  2. 10^-15 m
  3. 10^-2 m
  4. 10^-5 m

Answer: A) 10^-10 m

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

Discuss this question

Previous Page 2 of 5 Next

Practise Physical Quantities and Measurement MCQs

More Physics chapters