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question_answer1) What is the necessity of selecting some units as fundamental units?
question_answer2) How is SI a coherent system of units?
question_answer3) In defining the standard of length, (the prototype metre), we have to specify the temperature at which the measurement should be made. Are we justified in calling length a fundamental quantity, if another physical quantity (temperature) has to be specified in choosing a standard?
question_answer4) Do \[\overset{\text{o}}{\mathop{\text{A}}}\,\] and AU stand for the same unit of length?
question_answer5) Why is it convenient to express the distances of stars in terms of light year rather than in metre or kilometre?
question_answer6) Comment on the statement: "To define a physical quantity for which no method of measurement is given or known has no meaning."
question_answer7) Is the measure of an angle dependent upon the unit of length?
question_answer8) What is meant by angular diameter of the moon? What is its value?
question_answer9) For a given base line, which will show a greater parallax - a distant star or a nearby star?
question_answer10) Why is parallax method not useful for measuring the distances of stars more than 100 light years away?
question_answer11) What is the difference between mN, Nm and nm?
question_answer12) Do all physical quantities have dimensions? If no, name three physical quantities which are dimensionless.
question_answer13) If 'slap' times speed equals power, what will be the dimensional equation for 'slap'?
question_answer14) Write the dimensions and SI unit of linear momentum.
question_answer15) What is the basis of the principle of homogeneity of dimensions?
question_answer16) If \[~x\text{ }=\text{ }a\text{ }+\text{ }bt+c{{t}^{2}},\] where \[x\] is in metre and t in second; then what is the unit of c?
question_answer17) What are the dimensions of a and b in the relation: \[~\mathbf{F}\text{ }=a+bx,\] where F is force and \[x\] is distance?
question_answer18) Name two physical quantities having the dimensions \[[M{{L}^{2}}{{T}^{-2}}]\].
question_answer19) Write three physical quantities having dimensions \[[M{{L}^{-1}}{{T}^{-2}}]\]
question_answer20) If the units of force and length each are doubled, then how many times would the unit of energy be affected?
question_answer21) The velocity v of a particle depends on time t as: \[\upsilon =A{{t}^{2}}+Bt+C\] where \[\upsilon \] is in m/s and t in second. What are the units of A, B and C?
question_answer22) Can a quantity have dimensions but still has no units?
question_answer23) Can a quantity have different dimensions in different systems of units?
question_answer24) Can a quantity have units but still be dimensionless?
question_answer25) Does the magnitude of a physical quantity depend on the system of units chosen?
question_answer26) Justify L + L = L and L - L = L.
question_answer27) Can there be a physical quantity that has no units and no dimensions?
question_answer28) Can an instrument be called precise with-out being accurate? Can it be accurate without being precise?
question_answer29) Which of the following length measurements is (i) most precise and (ii) least precise? Give reason (i) \[l\mathbf{ =5cm}\] (ii) \[l\mathbf{=5}\mathbf{.00cm}\] (iii) \[\mathbf{5}.\mathbf{000}\text{ }\mathbf{cm}\] (iv) \[\mathbf{5}.\mathbf{000}\text{ }\mathbf{cm}\] (\[\upsilon \])\[~\mathbf{5}.\mathbf{00000}\text{ }\mathbf{cm}\].
question_answer30) Which of the following readings is the most accurate : (i) \[\mathbf{~5000 m}\] (ii) \[\mathbf{5\times 1}{{\mathbf{0}}^{\mathbf{2}}}\mathbf{m}\] (iii) \[\mathbf{5\times 1}{{\mathbf{0}}^{\mathbf{3}}}\mathbf{m}\]?
question_answer31) Which quantity in a given formula should be measured most accurately?
question_answer32) Which of the following measurements is more accurate and why? (a) \[\mathbf{0}\mathbf{.0002 g}\] (b) \[\mathbf{20}\mathbf{.0 g}\]
question_answer33) Why do we treat length, mass and time as basic or fundamental quantities in mechanics?
question_answer34) \[SI\] is a rational system of units while mks system is not so. Justify.
question_answer35) Why it became necessary to redefine metre on atomic standard?
question_answer36) What are the advantages of defining metre in terms of the wavelength of light radiation?
question_answer37) Give reasons why is platinum iridium alloy used in making prototype metre and kilogram.
question_answer38) Suggest a distance corresponding to each of the following order of length: (i) \[{{10}^{7}}\mathbf{m}\] (ii) \[\mathbf{1}{{\mathbf{0}}^{\mathbf{4}}}\mathbf{m}\] (Hi) \[{{10}^{2}}\mathbf{m}\] (iv) \[\mathbf{1}{{\mathbf{0}}^{\mathbf{-}}}^{\mathbf{3}}\mathbf{m}\] (v) \[\mathbf{1}{{\mathbf{0}}^{\mathbf{-6}}}\mathbf{m}\] (vi) \[\mathbf{1}{{\mathbf{0}}^{\mathbf{-14}}}\mathbf{m}\].
question_answer39) Suggest an indirect method for measuring the height of a tree on a sunny day.
question_answer40) What is the basic principle of alpha particle scattering method for estimating the size of the nucleus?
question_answer41) If the velocity of light is taken as the unit of velocity and one year as the unit of time, what must be the unit of length? What is it called?
question_answer42) What is common between bar and torr?
question_answer43) Distinguish between accuracy and precision.
question_answer44) Which of the following measurements is most accurate and which is most precise : (i) 4.00mm (ii) 4.00 cm (iii) 4.00 m (iv) 40.00 m?
question_answer45) Two clocks are being tested against a standard clock located in a national laboratory. At 12:00:00 noon by the standard clock, the readings of the two clocks are: Day Clock 1 Clock 2 Monday \[\text{12}:00:0\text{5}\] \[\text{1}0:\text{15}:0\text{6}\] Tuesday \[\text{12}:0\text{1}:\text{15}\] \[\text{1}0:\text{14}:\text{59}\] Wednesday \[\text{11}:\text{59}:0\text{8}\] \[\text{1}0:\text{15}:\text{18}\] Thursday \[\text{12}:0\text{1}:\text{5}0\] \[\text{1}0:\text{15}:0\text{7}\] Friday \[\text{11}:\text{59}:\text{15}\] \[\text{1}0:\text{14}:\text{53}\] Saturday \[\text{12}:0\text{1}:\text{3}0\] \[\text{1}0:\text{15}:\text{24}\] Sunday \[\text{12}:0\text{1}:\text{19}\] \[\text{1}0:\text{15}:\text{11}\] If you are doing an experiment that requires precision time interval measurements, which of the two clocks will you prefer?
question_answer46) For the determination of ?g? using a simple pendulum, measurements of \[l\]and \[T\] are required. Error in the measurement of which of these will have larger effect on the value of ?g? thus obtained and why? What is done to minimize this error?
question_answer47) Magnitude of force F experienced by a certain object moving with speed \[\upsilon \] is given by \[F=K{{\upsilon }^{2}}\], where \[K\] is a constant. Find the dimensions of \[K\].
question_answer48) The SI unit of energy is\[J=kg{{m}^{2}}{{s}^{-2}},\]that of speed \[\upsilon \] is \[\mathbf{m}{{\mathbf{s}}^{-\mathbf{1}}}\]and acceleration a is \[\mathbf{m}{{\mathbf{s}}^{-\mathbf{2}}}\]. Which of the formulae for kinetic energy (K) given below can you rule out on the basis of dimensional arguments (m stands for the mass of the body) : (a) \[K={{m}^{2}}{{\upsilon }^{3}}\] (b) \[K=\left( 1/2 \right)m{{\upsilon }^{2}}\] (c) \[~K=ma\] (d) \[~K=\text{ }(\mathbf{3}\text{ }/16)m{{\upsilon }^{2}}\] (e) \[K=(\mathbf{1}/\text{ 2})m{{\upsilon }^{2}}+\text{ }ma\]
question_answer49) Using the principle of homogeneity of dimensions, find which of the following is correct: (i) \[{{T}^{2}}=4{{\pi }^{2}}{{r}^{2}}\] (ii) \[{{T}^{2}}=\frac{4{{\pi }^{2}}{{r}^{3}}}{G}\] (iii) \[{{T}^{2}}=\frac{4{{\pi }^{2}}{{r}^{3}}}{GM}\] where T is time period, G is gravitational constant, M is mass and r is radius of orbit.
question_answer50) The mean value of period of oscillation of a simple pendulum in an experiment is\[\mathbf{2}.\mathbf{825}\text{ }\mathbf{s}\]. The arithmatic mean of all the absolute errors is\[\mathbf{0}.\mathbf{11}\text{ }\mathbf{s}\]. Round off the period of simple pendulum to appropriate number of significant figures. Give reasons.
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