Question 28. Toppr provides free study materials, 1000+ hours of video lectures, last 10 years of question papers for free. (b) A Jet plane moves with a speed greater than that of a super fast train. NCERT Solutions for Class 11-science Physics CBSE, 3 Motion in a Straight Line. Nuclear mass density = Mass of nucleus/Volume of nucleus Answer: Question 2. Question 7. Answer: 1 micron (1 p) = 10-6 m Reynold’s number NR (a dimensionless quantity) determines the condition of laminar flow of a viscous liquid through a pipe. We can estimate the area of the head. Answer:  As magnification, m =thickness of image of hair/ real thickness of hair = 100 So, the nuclear mass density is nearly 50 million times more than the atomic mass density for a sodium atom. NCERT solutions provide a strong foundation for every chapter. A laser light beam sent to the moon takes 2.56 s to return after reflection at the Moon’s surface. Answer: Question 5. Across Sketch the cross section of soil and label the various layers. If d be the distance of Moon from the earth, the time taken by laser signal to return after reflection at the Moon’s surface. km h-2 30. (a) The size of an atom is much smaller than even the sharp tip of a pin. (e) This is a correct statement. [Y] = [ML-1T–2] Mass density of Sun is in the range of mass densities of solids/liquids and not gases. You can also download here the NCERT Solutions Class 11 Physics chapter 2 Units And Measurement in PDF format. (b) Measure the depth of an empty boat in water. E, m, 1 and G denote energy, mass, angular momentum and gravitational constant respectively.Determine the dimensions of El2/m5G2. Ans : $$\begin{array}{l}{\text { Distance between Sun and Earth }} \\ {=\text { Speed of light in vacuum } x \text { time taken by light to travel from Sim to Earth }=3 \times 10^{8} \mathrm{m} / \mathrm{s} \times 8} \\ {\min 20 \mathrm{s}=3 \times 10^{8} \mathrm{m} / \mathrm{s} \times 500 \mathrm{s}=500 \times 3 \times 10^{8} \mathrm{m} \text { . }} A book with many printing errors contains four different formulas for the displacement y of a particle undergoing a certain periodic motion: If you have any problem in finding the correct answers of Physics Part I Textbook then you can find here. Volume of hydrogen molecule = 4/3 πr3 Long Answer Type Questions Volume of one mole atom of sodium, V = NA .4/3 π R3 Question 24. Its density is ______g a-n 30r ______kg m⁻⁵. NCERT Solutions Class 11 Physics with Chapter-wise, detailed are given with the objective of helping students compare their answers with the example. Answer: The distance at which a star would have annual parallax of 1 second of arc. Pages. \(\begin{array}{l}{1 \mathrm{s}=\frac{1}{\gamma}=\gamma^{-1}} \\ {1 \mathrm{s}^{2}=\gamma^{-2}} \\ {1 \mathrm{s}^{-2}=\gamma^{2}}\end{array}$$ Answer: No. (c) modulus of elasticity (d) all the above Now take a large sized trough filled with water. Density of water = 1 g/cm³ Let us further assume that the hair on the head are uniformly distributed. NCERT Solutions Class 11 can be extremely useful in understanding the methods of framing answers and writing them in a way that exhibits the student’s analysis of phenomena supported by facts. (a) The size of an atom is much smaller than even the sharp tip of a pin. Question 2. Find the Young’s modulus of the material of the wire from this data. Question 2. (c) the wind speed during a storm Question 15. (d) The air inside this room contains more number of molecules than in one mole of air. NCERT Solutions for Class 11 Physics Chapter 2 Units and Measurements are part of NCERT Solutions for Class 11 Physics. Question 17. Question 19. Question 2. The distance of the Sun from the Earth is 1.496 x 1011 m (i.e., 1 A.U.). Answer: Here area of the house on slide = 1.75 cm2 = 1.75 x 10-4 m2 and area of the house of projector-screen = 1.55 m2 Answer:  Assume that the nucleus is spherical. Vidyakul gives the NCERT Solutions for class 11 physics in the PDF. Answer:  From parallax method we can say The Reynold’s number nR for a liquid flowing through a pipe depends upon: (i) the density of the liquid ρ, (ii) the coefficient of viscosity η, (iii) the speed of flow of the liquid v, and (iv) the f radius of the tube r.Obtain dimensionally an expression for nR. Solving these equations, we get The number of hair on the head is clearly the ratio of the area of head to the cross-sectional area of a hair. Parallax angle subtended by the star Alpha Centauri at the given basis θ = 1.32 x 2 = 2.64″. (b) A screw gauge has a pitch of 1.0 mm and 200 divisions on the circular scale. The number of particles crossing per unit area perpendicular to x-axis in unit time N is given by N= -D(n2-n1/x2-x1), where n1 and n2 are the number of particles per unit volume at x1 and x2 respectively. Measure the length of this coil, mode by the thread, with a metre scale. $$\begin{array}{l}{ 1 \mathrm{cm} 3=10-6 \mathrm{m} 3} \\ {\text { Hence, the volume of a cube of side } 1 \mathrm{cm} \text { is equal to } 10-6 \mathrm{m} 3 \text { . i. e., [L1 T-1] = dimensionless, which is incorrect. Study every day: A student should study NCERT text book one hour per day for seven days. If distance of Venus be d, then t = 2d/c One mole contains 6.023 x 1023 molecules. The dimensions of diffusion constant D are Think of ways by which you can estimate the following (where an estimate is difficult to obtain, try to get an upper bound on the quantity): These objects (known as quasars) have many puzzling features, which have not yet been satisfactorily explained. (a) atoms are very small objects From the table of fundamental constants in this book, try to see if you too can construct this number (or any other interesting number you can think of). Download Class 11 Physics NCERT Solutions in pdf free. = 0.5238 x 10-30 m3 Answer: Question 2. (c) Speed of vehicle = 18 km/h = 18 x 1000/3600 m/s (a) (αa – βb +γc)% (b) (αa + βb +γc)% According to Avagadro’s hypothesis, one mole of hydrogen contains 6.023 x 1023 atoms. Linear magnification. }}\end{array}$$ kg m-3. Correcting the L.H.S., we. Answer:  As Area = (4.234 x 1.005) x 2 = 8.51034 = 8.5 m2 (a)$$1 \mathrm{cm}=\frac{1}{100} \mathrm{m}$$ Obtain a relation between the distance travelled by a body in time t, if its initial velocity be u and accelerationf. Fill in the blanks Parallax angle subtended by 1 parsec distance at this basis = 2 second (by definition of parsec). Question 2. If the angular diameter of the Sun is 2000″, find the diameter of the Sun. unit of time is ys. \begin{aligned}(b) 3 \mathrm{ms}^{-2} &=\frac{3 \times 10^{-3} \mathrm{km}}{\left(\frac{1}{3600}\right)^{2} \mathrm{h}^{2}}=3 \times 3600 \times 3600 \times 10^{-3} \mathrm{km} \mathrm{h}^{-2} \\ &=3.888 \times 10^{4} \mathrm{km} \mathrm{h}^{-2} \end{aligned} Hence more reliable result can be obtained. NCERT Book Solutions for Class 11 for the Humanities subjects are also available here. What do you mean by order of magnitude? Answer the following: =11.3 x 103 kg m-3 [1 kg =103 g,1m=102 cm] Suppose we employ a system of units in which the unit of mass equals a kg, the unit of length equals j8 m, the. Relative error in the volume of block. NCERT Solutions for Class 11. If A be the base area of the boat, then volume of water displaced by boat, V1 = Ad2 Answer: Young’s modulus of the material of the wire is given as. Fill in the blanks by suitable conversion of units: NCERT Solutions for Class 6, 7, 8, 9, 10, 11 and 12. Do A and A.U. Answer: Volume of one hydrogen atom = 4/3 πr3 (volume of sphere) Compare it with the average mass density of a sodium atom obtained in Exercise 2.27. Therefore, time needs more careful measurement. NCERT SOLUTION, CLASS 11, PHYSICS, PHYSICAL, CBSE BOARD . 1 A.U. Here we have given NCERT Solutions for Class 11 Physics Chapter 2 … = 28.38 x 1024 m = 2.8 x 1025 m or 2.8 x 1022 km. The nearest divisions would not clearly be distinguished as separate. Consider a class room of size 10 m x 8 m x 4 m. Volume of this room is 320 m3. 25. Question 2. Answer:  —> Stress and Young’s modulus. 9. (iv) Kinetic energy (v) Gravitational constant (vi) Permeability The distance of the Moon from the Earth has been already determined very precisely using a laser as a source of light. Define parsec. 28. A famous relation in physics relates ‘moving mass’ m to the ‘rest mass’ m0 of a particle in terms of its speed v and the speed of light c. (This relation first arose as a consequence of special relativity due to Albert Einstein). In the new system, the speed of light in vacuum is unity. $$\begin{array}{l}{1 \mathrm{s}=\frac{1}{\gamma}=\gamma^{-1}} \\ {1 \mathrm{s}^{2}=\gamma^{-2}} \\ {1 \mathrm{s}^{-2}=\gamma^{2}}\end{array}$$ If the percentage errors in measurements of a, b and c are ± 1%, ±2% and ± 1.5% respectively, then calculate the maximum percentage error in value of x obtained. Answer: RADAR stands for ‘Radio detection and ranging’. The farthest objects in our Universe discovered by modem astronomers are so distant that light emitted by them takes billions of years to reach the Earth. The baseline AB is the line joining the Earth’s two locations six months apart in its orbit around the Sun. $$\mathrm{But}, 1 \mathrm{cm} 3=1 \mathrm{cm} \times 1 \mathrm{cm} \times 1 \mathrm{cm}=\left(\frac{1}{100}\right) \mathrm{m} \times\left(\frac{1}{100}\right) \mathrm{m} \times\left(\frac{1}{100}\right) \mathrm{m}$$ length (1) = 5.12 cm P.A.M. Dirac, a great physicist of 20th century found that from the following basic constants, a number having dimensions of time can be constructed: Answer: The line joining a given object to our eye is known as the line of sight. This is due to the fact that the probability (chance) of making a positive random error of a given magnitude is equal to that of making a negative random error of the same magnitude. The value of d directly gives the wind speed. The heat dissipated in a resistance can be obtained by the measurement of resistance, the current and time. Applications engineer, data analyst, accelerator operator and aeronautical engineering are some of the prominent employment areas after completing graduation with physics as a major. (a) 1 kg m2 s-2 = …. Angular diameter of the moon, θ= Angular diameter of the sun Volume of nucleus Answer: The measured (nominal) volume of the block is, Area= l x b Name four units used in the measurement of extremely short distances. NCERT Solutions for Class 11. If instead of mass, length and time as fundamental quantities, we choose velocity, acceleration and force as fundamental quantities and express their dimensions by V, A and F respectively, show that the dimensions of Young’s modulus can be expressed as [FA2 V-4]. = 4/3 x 3.142 x (6.37 x 106)3m3 Think of different examples in modem science where precise measurements of length, time, mass etc., are needed. Obtain the dimensional formula for coefficient of viscosity. Answer: N m-1 s2 is nothing but SI unit of mass i.e., the kilogram. In view of this, reframe the following statements wherever necessary: Name two pairs of physical quantities whose dimensions are same. If the length and time period of an oscillating pendulum have errors of 1% and 2% respectively, what is the error in the estimate of g? The distance travelled by light in one year (i.e., 365 days = 3.154 x 107 s) is known as light year. A body travels uniformly a distance of (13.8 ± 0.2) m in a time (4.0 ± 0.3) s. What is the velocity of the body within error limits? = Speed of light in vacuum x time taken by light to travel from Sim to Earth = 3 x 108  m/ s x 8 min 20 s = 3 x 108 m/s x 500 s = 500 x 3 x 108 m. What is the distance in km of a quasar from which light takes 3.0 billion years to reach us? 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