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Class 11 Important Questions for Physics - Measurements

Here you can get Class 11 Important Questions for Physics based on NCERT Textbook for Class XI. Physics Class 11 Important Questions are very helpful to score high marks in board exams. Here we have covered Important Questions on Measurements for Class 11 Physics subject.

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Class 11 Important Questions for Physics - Measurements

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  1. Measurements INFOMATICA ACADEMY CONTACT: 9821131002/9029004242 ❖ ❖Illustrative Examples 1)Force experienced by charge ‘q’ moving with velocity ‘v’ in a magnetic field ‘B’ is given by F = qvB. Find the dimensions of magnetic field. (Ans. ) 2)Find the conversion factor between S.I. unit and CGS unit of density. (Ans. ) 3)Check whether the equation is dimensionally correct, (Ans. ) Each term does not have the same dimensions hence the equation is dimensionally incorrect. 4)The frequency (n) of vibration of a wire under tension depends upon the tension (T), mass per unit length (m) and vibrating length of the wire. Using dimensional analysis, obtain the dependence of frequency on these quantities.(Ans. ) 5)The radius of a nucleus of mass number ‘A’ is given by Find the order of magnitude of radius for a nucleus with ( Ans. Order of magnitude is m.) 6)The length of a metal plate was measured using a vernier callipers of least count 0.01 cm. The measurements made were 3.11 cm, 3.13 cm, 3.14 cm and 3.14 cm. Find the mean length, the mean absolute error and the percentage error in the measurement of length. Data : ( Ans. ) 7)Find the percentage error in kinetic energy of a body of mass and moving with a velocity of cm/s. (Ans. ) Data : ❖ ❖Theory Questions F.Y.J.C. Science Measurements

  2. INFOMATICA ACADEMY 1) What is the need for measurement of a physical quantity? CONTACT: 9821131002/9029004242 2) What is meant by unit of a physical quantity? 3) State different types of systems of units. 4) What is S.I. system of units? Explain its need. 5) What are fundamental quantities and fundamental units? State two examples of fundamental quantities and their S.I. and C. G.. S. units. 6) What are derived quantities and derived units? State two examples. 7) Explain the method to measure length, mass and time. 8) Define dimensions and dimension equation. Give two examples. 9) State the uses of dimensional analysis. Explain each use with the help of an example. 10)Explain with example the term ‘order of magnitude of a physical quantity’. 11)State the rules for determining significant figures. 12)Explain in brief, accuracy and errors in measurements. 13)Explain different types of errors in measurements with remedies. 14)Define: (i) Most probable value, (ii)Absolute error, (iii)Relative error, (iv)Percentage error. 15)What is scope of physics. 16)Define unit. Give its ideal proper has. 17)Conventions for writing S.I. units. 18)Define: (i)Significant figure (ii)Error (iii)Mean value (iv)Mean absolute error 19)State the essential characteristics of a good unit. 20)Explain the advantages of S.I. system of unit. 21)Classify the following quantities into fundamental and derived quantities: Length, Velocity, Area, Electric current, Acceleration, Time, Force, Momentum, Energy, Temperature, Mass, Pressure, Magnetic induction, Density. 22)Classify the following units into fundamental, supplementary and derived units: newton, metre, candela, radian, hertz, square metre, tesla, ampere, kelvin, volt, mol, coulomb, farad, steradian. 23)Define parallactic angle. F.Y.J.C. Science Measurements

  3. INFOMATICA ACADEMY 24)A book with many printing errors contains four different formulae for the CONTACT: 9821131002/9029004242 displacement y of a particle undergoing a certain periodic function: (i) (iii) (ii) (iv) Here, a is maximum displacement of particle, v is speed of particle, T is time period of motion. Rule out the wrong formulae on dimensional grounds. (NCERT) 25)State principle of homogeneity. Use this principle and find conversion factor between the units of the same physical quantity in two different systems of units. OR Explain how the principle of homogeneity can be used to find the conversion factor between the units of the same physical quantity in two different systems of units. 26)Explain the use of dimensional analysis to check the correctness of a physical equation. 27)Explain the use of dimensional analysis to find the conversion factor between units of same physical quantity into different systems of units.OR Find the conversion factor between the S.I. and the C.G.S. units of force using dimensional analysis. 28)Time period of a simple pendulum depends upon the length of pendulum (I) and acceleration due to gravity (g). Using dimensional analysis, obtain an expression for time period of simple pendulum. 29)State the drawbacks of dimensional analysis. 30)Determine the order of magnitude of the following physical quantities. i.Radius of the earth ii. Mass of the earth iii.Charge on electron iv.One year v.Universal gravitational constant. 31)Find the number of significant figures in the following numbers. i.25.42 ii. 0.004567 iii. 35.320 iv. 4.56 v. 1.609 vi.91.000 32)Explain the rules for rounding-off the number of the significant figures with examples. 33)What is an error? Classify errors into different categories. F.Y.J.C. Science Measurements

  4. INFOMATICA ACADEMY 34)What is instrumental (constant) error? Explain the cause and remedies of CONTACT: 9821131002/9029004242 instrumental errors. 35)What is systematic error? Write down the cause and minimization of systematic error? 36)What is personal error? Give its remedies error. 37)What is random error (accidental)? How can it be minimized? 38)State general methods to minimize effect of errors. 39)What are mistakes? Explain causes of mistakes and their remedies. 40)Distinguish between Mistakes and Errors in measurements. 41)If the error in 'a' is a then find the percentage error in: i. ii. a – b iii. ❖ ❖Textbook Problems 1)Find the dimensions of (i) Power, (ii) Force and (iii) Permittivity of vacuum . (Ans. (i) (ii) (iii) ) 2)Using dimensions, show that 1 joule = 107 erg. 3)If length ‘L’, force ‘F’ and time ‘T’ are taken as fundamental quantities. What would the dimensional equation of mass and density? (Ans. ) 4)The hydrostatic pressure ‘P’ of a liquid column depends upon the density ‘d’, height ‘h’ of liquid column and also an accleration ‘g’ due to gravity. Using dimensional analysis, derive formula for pressure P. (Ans : P = hdg). 5)Derive an expression of kinetic energy of a body of mass ‘m’ and moving with velocity ‘v’, using dimensional analysis. (Ans : kmv2). 6)State the order of magnitude of the following: (a)Acceleration due to gravity g = 9.81 m/s2 (b)The gravitation constant (c)The period of rotation of the earth about its own axis. (Ans. (a) (b) (C) ). 7)Determine the number of significant figures in the following measurement : (a) (b) (c) (d) (Ans : (a) 4, (b) 4, (c) 3 (d) 5.) F.Y.J.C. Science Measurements

  5. INFOMATICA ACADEMY 8)An object was weighed by a physical balance and following readings were obtained: CONTACT: 9821131002/9029004242 5.04 g; 5.06 g; 4.97g; 5.00g; 4.93g. Find (i) Mean value, (ii) Absolute error, (iii) Percentage error. (Ans : (i) 5.00 g, (ii) 0.04g, (iii) 0.8%.) 9)Check the correctness of formula by using dimensional analysis. 10)A calorie is a unit of heat or energy and it is equal to about 4.2 J where 1 J = 1 kg m2 s-2. Suppose, we employ a system of units in which unit of mass equals kg, the unit of length equals m, and the unit of time is s. Show that a calorie has a magnitude of 4.2 in terms of the new units. (Ans. The magnitude of a calorie in terms of the new units is 4.2 ) 11)Density of oil is 0.8 g cm-3 in C.G.S. unit. Find its value in S.I. units. (Ans. Density of oil in S.I unit is 0.8 103 kg m-3) 12)Assume that the speed (v) of sound in air depends upon the pressure (P) and density ( ) of air, then use dimensional analysis to obtain an expression for the speed of sound. 13)The value of G in C.G.S system is 6.67 x 10-8 dyne cm2g-2 Calculate its value in S.I. system. (Ans. Value of G in S.I. system is 6.67 ) 14)Add 7.21, 12.141 and 0.0028 and express the result to an appropriate number of significant figures. (Ans. Corrected rounded off sun, is 19.35.) 15)The length, breadth and thickness of a rectangular sheet of metal are 4.234 m, 1.005 m and 2.01 cm respectively. Give the area and volume of the sheet to correct significant figures. (Ans. i. Area of sheet to correct significant figures is 8.510 m2. ii. Volume of sheet to correct significant figures is 0.085 m3.] 16)The mass of a box measured by a grocer's balance is 2.3 kg. Two gold pieces of masses 20.15 g and 20.17 g are added to the box. What is (i) the total mass of the box? (ii) the difference in the masses of the pieces to correct significant figures? (Ans: i. The total mass of the box to correct significant figures is 2.3 kg. ii. The difference in the masses to correct significant figures is 0.02 g.) 17)Find the order of magnitude of force exerted by the sun on the earth. Mass of the sun : 1.99 1030 kg, Mass of earth : 5.97 1024 kg, Distance between Earth and the Sun = 1.49 1011 m, G = 6.67 10-11 Nm2/kg2 (Ans. The order of magnitude of the force exerted by the sun on the earth is 1022 N.) F.Y.J.C. Science Measurements

  6. INFOMATICA ACADEMY 18)In an experiment to find the density of a solid, the mass and volume of the solid CONTACT: 9821131002/9029004242 were found to be 400.3 0.02 g and 75.6 0.01 cm3 respectively. Find the percentage error in the determination of its density. (Ans. The percentage eror in the determination density is 0.018%) 19)Find the percentage error in energy where m = (52.4 0.2) kg and v = (25.6 0.1) m/s. (Ans : The percentage error in energy is0.16 %.] 20)In an experiment, width of given object was found to be 1.55 cm, 1.54 cm, 1.53 cm, 1.52 cm, 1.49 cm in successive trials. Calculate mean absolute error? relative error and percentage error. (Ans. i. The mean absolute error is 0.0168 cm. ii. The relative error is 0.011 cm. iii. The percentage error is 1.1 %) 21)An object was weighed by a physical balance and following readings were obtained: 5.04 g, 5.06 g, 4.97 9, 5.00 g, 4.93 g. Find i. Mean value ii. Mean absolute error iii. Percentage error. (Ans. i.The mean value is 5.00 g. ii. The mean absolute error is 0.04 g. iii. The percentage error is 0.8%) ❖ ❖Practice Problems ➢ ➢Type-I : Problems based on Dimensional analysis 1.The acceleration due to gravity of a place is 9.8 ms-2. Find its value in km h-2. (Ans. 127008 km h-2) 2.If the value of atmospheric pressure is 106 dyne cm in CGS system, find its value in S.I. system. (Ans. 2.105 Nm-2) 3.Check the correctness of the relation , where r is the torque acting on a body, I is the moment of inertia and is angular acceleration. 4.Check the correctness of 5.Assuming that the mass M of the largest stone that can be moved by a flowing river depends upon 'v' the velocity, 'p' the density of water and on 'g' the acceleration due to gravity. Show that M varies with sixth power of the velocity of flow. 6.Assuming that the critical velocity vc of a viscous liquid flowing through a capillary tube depends only upon the radius r of the tube, density and the coefficient of viscosity of the liquid, find the expression for critical velocity. [Ans. ] ➢ ➢Type-II : Order of magnitude and significant figures F.Y.J.C. Science Measurements

  7. INFOMATICA ACADEMY 7.Find the order of magnitude of following data. CONTACT: 9821131002/9029004242 i.height of a tower 4325 m (Ans. 103 m ) ii.weight of a car 789 kg (Ans. 103 Kg) iii.Charge on electron 1.6 10-19 C (Ans. 10-19 C) 8.Round off the following numbers as indicated i.15.654 upto 3 digits ii.1426 upto 5 digits iii.5.996 105 upto 3 digits (Ans. i. 15.7 ii.14260 iii.6.00 ) 9.Add 3.8 10-6 and 4.2 10-5 with due regards to significant figures. [Ans. 4.6 ] 10.The diameter of a sphere is 2.78m. Calculate its volume with due regards to significant figures. [Ans. 11.25 m3] ➢ ➢Type-III : Errors in measurement 11.Two different masses are determined as (23.7 0.5) g and (17.6 0.3) g. What is the sum of their masses? (Ans. 41.3 0.8 g ) 12.The lengths of two rods are recorded as l1: (25.2 0.1) cm and l2 (16.8 0.1) cm. Find their combined length. (Ans. 42.0 0.2 cm) ➢ ➢Type-IV : Miscellaneous 13.The length of a rod as measured in an experiment was found to be 2.48 m, 2.46 m,2.49 m, 2.50 m and 2.48 m. Find the mean absolute error, relative error and percentage error. (Ans. 0.01 m, 0.004 m 0.4 % ) ❖ ❖Multiple Choice Questions 1.Which of the following is the fundamental unit? (A)Length. force. Time (C) Mass, volume, height (B)Length, mass, time (D) Mass, velocity, pressure 2.S.I. unit of energy is joule and it is equivalent to (A)106 erg (B) 10-7 (C) 107 erg (D) 105 erg 3.Which of the following pairs are similar? (A)work and power (C) force and power (B)momentum and energy (D) work and energy 4.Which of the following is the moment of a force ? (A)[M1L1T-2] (B) [M1L2T-2] (C) [M1L-1T-2] (D) [M1L1T-1] F.Y.J.C. Science Measurements

  8. INFOMATICA ACADEMY 5.The dimension of elastic constant is CONTACT: 9821131002/9029004242 (A)[M1L2T-2] (B) [M-1L2T-2] (C)[M-1L2T-2] (D)[M-1L-1T-1] 6.The dimension of angular velocity is (A)[M1L1T-1] (B) [M1L3T-1] (C) [M0L0T-1] (D) [M1L-1T-1] 7.The dimension of power is (A)[M1L2T-3] (B) [M1L2T-1] (C) [M1L2T-1] (D)[M1L-2T-3] 8.Which of the following is the proper combination for force? (A)Kg (B) meter/s2 (C) Kg m m/s2 (D)Kg m/s2 9.A physical quantity may be defined as (A) the one having dimension. (C) that which has weight. (B) that which is immeasurable. (D) that which has mass. 10.[M1L1T-1] is an expression for (A)Force (B) Energy (C)pressure (D)momentum 11.Dimensions of sin is (A)[L2] (B) [M] (C)[ML] (D)[M0L0T0] 12.Dimensions of surface tension is (A)[M1L-1T-1] (B) [M1L0T-2] (C)[M1LT-1] (D)[M2L2T-1] 13.Dimensions of frequency is (A)[M-1L3T-2] (B) [M1L1T-1] (C)[M0L0T-1] (D)[M1L-2T-2] 14.The unit of energy is same as the unit of (A) power (B) momentum (C) Work (D)Force 15.Dyne-second stands for the unit of (A) force (B) momentum (C) energy (D) power 16.Which of the following quantities can be written as kg m2 A-2 s-3 in S.I. units? (A) resistance (B) inductance (C) capacitance (D) magnetic flux 17.Error in the measurement of radius of a sphere is 1%. Then error in the measurement of volume is (A)1% (B) 5% (C) 3% (D)8% 18.Three measurements are made as 18'425 cm, 7.21 cm and 5.0 cm. The addition should be written as (A)30.635 cm (B) 30.64 cm (C) 30.63 cm (D) 30.6 cm 19.Subtract 0.2 J from 1 .26 J and express the result with correct number of significant figures. (A)7.1 J (B) 7.06 J (C) 7.0 J (D) 7 J 20.The number of significant figure in 11.118 10-6 is (A)3 (B) 4 (C) 5 (D) 6 F.Y.J.C. Science Measurements

  9. INFOMATICA ACADEMY 21.Zero error of instrument introduces CONTACT: 9821131002/9029004242 (A)systematic error (C) personal error (B) random error (D) decimal error 22.Accuracy of measurement is determined by (A) absolute error (C) human error (B) percentage error (D) Personal error 23.What is the % error in measurement of time period of a pendulum, if maximum errors in measurements of length and 'g' ate 2% and 4olo respectively? (A)6% (B) 3% (C) 4% (D) 5% 24.When a current of (2.5 0.5) A flows through a wire, it develops a potential difference of (20 1) V. The resistance of wire is (A) (8 2) ohm (B) (8 1.5) ohm (C) (8 0.5) ohm (D) (8 3) ohm 25.A distance of about 50 cm is measured using metre stick having mm division. The percentage error is (A)0.2% (B) 0.4% (C)0.02% (D)0.002% 26.The distance of the planet from the earth is measured by (A) direct method (C) spherometer method (B) directly by metre scale (D) parallax method 27.The diameter of the paper pin is measured accurately by using (A) vernier callipers (C) metre scale (B) micrometer screw gauge (D) a measuring tape 28.For measurement of mass of subatomic particles, which of the following method is suitable? (A) Parallal method (B) Mass spectro graph (C) Method based on Newton's law of gravitation (D) Lever balance 29.An atomic clock makes use of (A) cesium-133 atom (C) cesium-123 atom (B) cesium-132 atom (D) cesium-131 atom 30.Dimensional equation for temperature gradient is (A)[M1L0T1K0] (B) [M0L-1T0K1] (C)[M0L-1T0K-1] (D) [M0L-1T0K-1] 31.The two stars S1 and S2 are located at distances d1 and d2 respectively. Also if d1 > d2 then following statement is true. (A)The parallax of S1 and S2 are same. (B)The parallax of S1 is twice as that of S2 (C) The parallax of S1 is greater than parallax of s2 F.Y.J.C. Science Measurements

  10. INFOMATICA ACADEMY (D) The parallax of S2 is greater than parallax of S1 CONTACT: 9821131002/9029004242 32.0.00849 contains significant figures. (A)6 (B)5 (C) 3 (D) 2 33.50.000 contains significant figures. (A) 5 (B) 3 (C) 2 (D) 1 34.3.310 102 has significant figures. (A) 6 (B) 4 (C) 2 (D) 1 35. Which of the following is NOT a fundamental quantity. (A)Temperature (B) Electric charge (C) Mass (D) Electric current 36.Which of the following is NOT a unit of time? (A) Hour (B) Nano second (C) Microsecond (D) Light Year 37.identify the pair, whose dimensions are equal (A) Torque and work (C) Force and stress (B) Stress and energy (D) Force and work 38.The Earth's radius is 6371 km. The order of magnitude of the Earth's radius is (A) 103 m (B) 109 m (C)107 m (D) 102 m ❖ ❖ Answers to Multiple Choice Questions 1.B 2.C 3.D 4.B 5.B 6.C 7.A 8.D 9.A 10.D 11.D 12.B 13.C 14.C 15.B 16.A 17.C 18.D 19.A 20.C 21.A 22.B 23.B 24.A 25.A 26.D 27.B 28.B 29.A 30.D 31.D 33.A 34.B 35.B 36.D 37.A 38.C . F.Y.J.C. Science Measurements

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