Tiêu đề 01. Units and Dimensions Med.pdf ✅

02. UNITS and DIMENSIONS [Medium] 1. The solid angle subtended by the periphery of an area 1 cm2 at a point situated symmetrically at a distance of 5 cm from the area is (a) 2 × 10-2 steradian (b) 4 × 10-2 steradian (c) 6 × 10-2 steradian (d) 8 × 10-2 steradian 2. In which year SI system of units was developed and recommended by General Conference on Weights and Measures? (a) 1951 (b) 1961 (c) 1971 (d) 1981 3. Which one of the following physical quantities is not a fundamental quantity? (a) Luminous intensity (b) Thermodynamic intensity (c) Electric current (d) Work 4. The SI unit of pressure gradient is (a) N m-2 (b) N m (c) N m-1 (d) N m-3 5. The relative density of lead is 11.3. Its density in SI unit is (a) 1.13 × 103 (b) 1.13 × 102 (c) 1.13 × 104 (d) 11.3 6. Which of the following physical quantities has same unit in all the three system of units? (a) Mass (b) Length (c) Time (d) None of these 7. Spot out the odd one (a) Calorie (b) Kilowatt hour (c) Joule (d) Watt 8. Which of the following units is not a base unit? (a) Metre (b) Candela (c) Ampere (d) Pascal 9. Which of the following system of units is not based on unit of mass, length and time? (a) CGS (b) FPS (c) MKS (d) SI 10. Match the Column I with Column II Column I Physical quantity Column II Name of unit (A) Conductance (p) Gray (B) Magnetic induction (q) Lumen (C) Absorbed dose (r) Tesla (D) Luminous flux (s) Siemens (a) A – s, B – r, C – p, D – q (b) A – p, B – q, C - r, D – s (c) A – q, B – p, C - s, D – r (d) A – r, B – s, C – p, D – q 11. In International System of units, there are seven base quantities whose units are defined. Which physical quantity has a prefix with its unit? (a) Mass (b) Thermodynamic temperature (c) Luminous intensity (d) Amount of substance 12. The speed of sound in water is (a) 330 m s-1 (b) 630 m s-1 (c) 1450 m s-1 (d) 2250 m s-1 13. Which one of the following statements is incorrect? (a) Direct and indirect methods are used for the measurement of physical quantities (b) Scientific notation and the prefixes are used to simplify numerical computation (c) A dimensionally correct equation need not be a correct equation (d) The SI units is based on six base units 14. The distance of the moon from the earth is about 60 times the radius of the earth. What will be diameter of the earth (approximately in degrees) as seen from the moon? (a) 10 (b) 20 (c) 40 (d) 60 15. Match the Column I with Column II Column I Column II (A) Distance between earth and sun (p) Micron (B) Interatomic distance in a solid (q) Fermi (C) Size of a nucleus (r) Light year (D) Wavelength of infrared laser (s) Angstrom (a) A – p, B – q, C – r, D – s (b) A – r, B – s, C – q, D – p (c) A – q, B – p, C - s, D – r (d) A – s, B – r, C – p, D – q 16. The vernier scale of a travelling microscope has 50 divisions which coincide with 49 main scale divisions. If each main scale division is 0.5 mm, then the least count of the microscope is (a) 0.01 cm (b) 0.5 mm (c) 0.01 mm (d) 0.5 cm 17. Light year is (a) Light emitted by the sun in one year (b) The time taken by light to travel from sun to earth (c) The distance travelled by light in free space in one year (d) The time taken by earth to go once around the sun 18. The sun’s angular diameter is measured to be 1920’’. The distance of the sun from the earth is 11 1.49610 m. What is the diameter of the sun? (a) 1.39 10 m 9  (b) 1.39 10 m 10  (c) 1.39 10 m 11  (d) 1.39 10 m 12  19. The ratio of one micron to one nanometer is (a) 103 (b) 10-3 (c) 10-6 (d) 10-9 20. Which of the following conversions is incorrect?
(a) 1 curie = 3.7 × 1010 s -1 (b) 1 barn = 10-25 m2 (c) 1 quintal = 100 kg (d) 1 litre = 10-3 m3 21. How many light years Alpha Centauri away from the Earth? (a) 1.29 (b) 2.29 (c) 3.29 (d) 4.29 22. Which one of the following instruments is not used for the measurement of length? (a) Atomic clock (b) Vernier calipers (c) Screw gauge (d) Spherometer 23. A new unit of length is chosen such that the speed of light in vacuum is unity. What is the distance between the sun and the earth in terms of the new unit if light takes 8 min and 20 s to cover this distance? (a) 300 (b) 400 (c) 500 (d) 600 24. The ratio of the volume of the atom to the volume of the nucleus is of the order of (a) 1010 (b) 1015 (c) 1020 (d) 1025 25. What is the volume occupied by one mole of an ideal gas at STP? (a) 10.4 L (b) 11.4 L (c) 22.4 L (d) 33.4 L 26. Light year is the unit of (a) Distance (b) Time (c) Speed (d) Intensity of light 27. What is the length of the are of circle of radius 30 cm which subtend an angle 6  at the centre? (a) 11.7 cm (b) 14.7 cm (c) 16.7 cm (d) 15.7 cm 28. Which of the following is the smallest unit? (a) Millimetre (b) Angstrom (c) Fermi (d) Metre 29. Which of the following is unitless quantity? (a) Pressure gradient (b) Displacement gradient (c) Force gradient (d) Velocity gradient 30. How many wavelengths of Kr86 are there in metre? (a) 1553164.13 (b) 1650763.73 (c) 2348123.73 (d) 652189.63 31. Which of the following is the most precise device for measuring length? (a) A vernier callipers with 20 divisions on the vernier scale coinciding with 19 main scale divisions (b) A screw gauge of pitch 1 mm and 100 divisions on the circular scale (c) A spherometer of pitch 0.1 mm and 100 division on the circular scalem (d) An optical instrument that can measure length to within a wavelength of light 32. The ratio of molar volume to atomic volume for 1 mole of hydrogen is (Take size of hydrogen molecule to be 1 A) (a) 4 7.110 (b) 6 7.110 (c) 10 7.110 (d) 8 7.110 33. Fathom is the unit to measure the (a) Speed of ship (b) Depth of sea (c) Distance of the ship (d) Speed of cyclone 34. 1 Parsec is approximately equal to (Where AU is astronomical unit) (a) 2 × 105 AU (b) 2 × 106 AU (c) 2 × 108 AU (d) 2 × 1010 AU 35. Which one of the following waves is used in SONAR? (a) Infrared (b) Ultraviolet (c) Ultrasonic (d) Light 36. If the size of bacteria is 1 micron, what will be the number of it in 1 m length? (a) One hundred (b) One crore (c) One thousand (d) One million 37. Which of the following properties of laser beam can be used to measure long distances? (a) It is very intense (b) It is highly monochromatic (c) It is an unidirectional beam of light (d) All of these 38. Which one of the following methods is used to measure distance of a planet or a star from the earth? (a) Echo method (b) Parallax method (c) Triangulation method (d) None of these 39. The order of magnitude of the diameter of the earth is (Diameter of the earth is 1.28 × 107 m) (a) 5 (b) 6 (c) 7 (d) 8 40. Astronomical unit (AU) is the distance between earth and the sun. 1 AU is equal to (a) 1.496 × 108 km (b) 9.46 × 1012 km (c) 3.084 × 1013 km (d) 4.596 × 1015 km 41. Which of the following is not unit of earth? (a) Angstrom (b) Fermi (c) Barn (d) Parsec 42. If the unit of force is 100 N, unit of length is 10 m and unit of time is 100 s, what is the unit of mass in this system of units? (a) 103 kg (b) 104 kg (c) 105 kg (d) 106 kg 43. The device used for measuring the mass of atoms and molecules is (a) Spring balance (b) Torsional balance (c) Mass spectrograph (d) Common balance 44. 10-3 gram is called (a) Kilogram (b) Milligram (c) Decigram (d) Microgram 45. Which of the following statements is incorrect regarding mass? (a) It is a basic property of matter (b) The SI unit of mass is kg
(c) The mass of an atom is expressed in u (d) It depends upon the temperature, pressure or location of the object in space 46. 1 unified atomic mass unit (1 u) is equal to (a) 1.66 × 10-25 kg (b) 1.66 × 10-27 kg (c) 1.66 × 10-29 kg (d) 1.66 × 10-31 kg 47. Match the Column I with Column II Column I Event Column II Time Interval (s) (A) Life time of an excited state of an atom (p) 1017 (B) Average human life span (q) 1011 (C) Age of Egyptian pyramids (r) 109 (D) Age of the universe (s) 10-8 (a) A – s, B – r, C – q, D – p (b) A – p, B – q, C – r, D – s (c) A – q, B – p, C – s, D – r (d) A – r, B – s, C – p, D – q 48. Light from the sun reaches the earth approximately in (a) 5 s (b) 50 s (c) 500 s (d) 0.5 s 49. One second is defined as (a) 1650763.73 periods of Krypton clock (b) 6521896 periods of krypton clock (c) 165076373 periods of cesium clock (d) 9192631770 periods of cesium clock 50. Which of the following statements in incorrect? (a) Every measurement by measuring instrument has some error (b) A measurement can have more accuracy but less precision and vice versa (c) Every calculated quantity that is based o measured values has some error (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 51. Which of the following time measuring devices is most precise? (a) A well clock (b) An atomic clock (c) A digital watch (d) A stop watch 52. Which of the following is the most precise instrument for measuring length? (a) Metre rod of least count 0.1 cm (b) Vernier calipers of least count 0.01cm (c) Screw gauge of least count 0.001 cm (d) None of these 53. The number of significant figures in the numbers 4.8000 × 104 and 48000.50 are respectively (a) 5 and 6 (b) 5 and 7 (c) 2 and 7 (d) 2 and 6 54. A cube has a side of length 1.2×10-2 m. Its volume upto correct significant figures is (a) 1.7 × 10-6 m3 (b) 1.73 × 10-6 m3 (c) 1.70 × 10-6 m3 (d) 1.732 × 10-6 m3 55. Which of the following statements is incorrect regarding significant figures? (a) All the non-zero digits are significant (b) All the zeros between two non-zero digits are significant (c) Greater the number of significant figures in a measurement, smaller is the percentage error (d) The power of 10 is counted while counting the number of significant figures 56. In an experiment, the period of oscillation of a simple pendulum was observed to be 2.63 s, 2.56 s, 2.42 s, 2.71 s and 2.80 s. The mean absolute error is (a) 0.11 s (b) 0.12 s (c) 0.13 s (d) 0.14 s 57. Which of the following physical quantities has a unit but no dimensions? (a) Relative velocity (b) Relative density (c) Strain (d) Angle 58. If P, Q, R are physical quantities, having different dimensions, which of the following combinations can never be a meaningful quantity? (a) R (P − R) (b) PQ – R (c) R PQ (d) R (PR Q ) 2 − 59. If, m, l and G denote energy, mass, angular momentum and gravitational constant respectively, the quantity         5 2 2 m G El has the dimensions of (a) Mass (b) Length (c) Time (d) Angle 60. Which of the following physical quantities has neither units nor dimensions? (a) Relative velocity (b) Relative density (c) Angle (d) Energy 61. A Dimensionless quantity (a) Never has a unit (b) Always has unit (c) May have a unit (d) Does not exit 62. Which of the following rations express pressure? (a) Volume Energy (b) Area Energy (c) Volume Force (d) Volume Mementum 63. The dimensions of Plank’s constant are the same as that of (a) Linear impulse (b) Work (c) Linear momentum (d) Angular momentum 64. Match the Column I with Column II Column I Units Column II Dimensional formulae (A) Pa s (p)   0 2 2 1 M L T K − − (B) N m K-1 (q)   3 1 MLT K − −
(C) J kg-1 K-1 (r)   1 1 ML T − − (D) W m-1 K-1 (s)   2 2 1 ML T K − − (a) A – q, B – p, C – r, D – s (b) A – p, B – q, C – s, D – r (c) A – r, B – s, C – p, D – q (d) A – s, B – r, C – q, D – p 65. Which of the following quantities has the SI unit kg m2 s -3 A-2 ? (a) Resistance (b) Inductance (c) Capacitance (d) Magnetic Flux 66. If power (P), surface tension (S) and Planck’s constant (h) are arranged so that the dimensions of time in their dimensional formulae are in ascending order, then which of the following is correct? (a) P, S, h (b) P, h, S (c) S, P, h (d) S, h, P 67. Which of the following sets have different dimensions? (a) Pressure, Young’s modulus, stress (b) Emf, potential difference, electric potential (c) Heat, work done, energy (d) Dipole moment, electric flux, electric field 68. Match the Column I with Column II Column I Physical quantity Column II Dimensional formula (A) Permittivity of free space (p)   0 0 1 M L T − (B) Radiant flux (q)   3 3 2 ML T A − − (C) Resistivity (r)   2 3 ML T − (D) Hubble constant (s)   1 3 4 2 M L T A − − (a) A – p, B – q, C – r, D – s (b) A – q, B – p, C – s, D – r (c) A – s, B – r, C – q, D – p (d) A – r, B – s, C – p, D – q 69. If A = 2.331 cm, B = 2 cm, then A + B = ? (a) 4.431 cm (b) 4.43 cm (c) 4.4 cm (d) 4 cm 70. A new system of units is proposed in which unit of mass is  kg, unit of length is  m and unit of time is  s. What will be value of 5 J in this new system? (a) 2 2 5 −   (b) 1 2 2 5   − − (c) 2 1 2 5 − − −    (d) 1 2 2 5 − −    71. If velocity of c, Plank’s constant h and gravitational constant G are taken as fundamental quantities then the dimensions of length will be (a) G ch (b) 5 c hG (c) 3 c hG (d) G hc 3 72. The displacement of a progressive wave is represented by y = A sin( t − kx ) where x is distance and t is time The dimensions of k  are same as those of (a) Velocity (b) Wave number (c) Wavelength (d) Frequency 73. Using the principle of homogeneity of dimensions, which of the following is correct? (a) GM 4 r T 2 3 2  = (b) 2 2 2 T = 4 r (c) G 4 r T 2 3 2  = (d) G 4 r T 2 3  = 74. According to special theory of relativity, the mass m of a particle moving with speed v is (Where m0 is the rest mass and c is the speed of light) (a) m = m0 (b) 2 2 0 c v m = m 1− (c) 2 2 0 1 c v m m − = (d)         = 1− −1 2 2 0 c v m m 75. Checking the correctness of equations using the method of dimensions is based on (a) The type of system (b) Equality of inertial frames of references (c) Principle of homogeneity of dimensions (d) None of these 76. If the value of atmospheric pressure is 106 dyne cm-2 , its value in SI units is (a) 104 N m-2 (b) 106 N m-2 (c) 105 N m-2 (d) 103 N m-2 77. The number of significant figures in 0.06900 is (a) 5 (b) 4 (c) 2 (d) 3 78. The sum of the numbers 436.32, 227.2 and 0.301 in appropriate significant figures is (a) 663.821 (b) 664 (c) 663.8 (d) 663.82 79. Which of the following pairs of physical quantities does not have same dimensional formula? (a) Work and torque (b) Angular momentum and Plank’s constant (c) Tension and surface tension (d) Impulse and linear momentum 80. Which of the following measurements is most precise? (a) 5.00 mm (b) 5.00 cm (c) 5.00 m (d) 5.00 km 81. The mean length of an object is 5 cm. Which of the following measurements is most accurate? (a) 4.9 cm (b) 4.805 cm (c) 5.25 cm (d) 5.4 cm 82. If momentum (p), area (A) and time (t) are taken to be fundamental quantities, then energy has the dimensional formula (a) [p1 A-1 t -1 ] (b) [p2 A1 t 1 ] (c) [p1 A-1/2 t 1 ] (d) [p1 A1/2 t -1 ]