Tiêu đề 8-properties-of-matter-.pdf ✅

Properties of Matter A system of rods is assembled such that each rod has a length l and cross-sectional areas S. The mode of heat transfer is conduction and the system is in steady state. The temperature of junction B is T and that of D is 2T. Now answer the following questions. 1. Temperature of junction A is : (A) 5 3 T (B) 2 3 T (C) 1.8T (D) 1.5T 2. Temperature of junction C is : (A) 5 3 T (B) 1.6T (C) 4 3 T (D) 1.5T 3. The rate of heat flow along DB is : (A) Zero (B) kTS l (C) 1 2 kTS l (D) 2 kTS l 4. Emissivity e is a property of surface. Suppose, for a surface emissivity e varies with Kelvin with temp. T as e = CT ( C is constant). If energy emission rate at temp. 600 K from the surface is 160 W, what will be the energy emission rate (in watt) at 300 K. (A) 320 (B) 5 (C) 32 (D) 16 5. Two identical blocks of metal are at 20∘C and 80∘C respectively. The specific heat of the material of the two blocks increases with temperature. Which of the following is true about the final temperature Tf when the two blocks are brought into contact (Assuming that no heat is lost to the surrounding) (A) Tf will be 50∘C (B) Tf wll be more than 50∘C (C) Tf will be less than 50∘C (D) Tf can be more than or less than 50∘C depending on the precise variation of the specific heat with temperature 6. A rectangular frame is to be suspended symmetrically by two strings of equal length on two supports figure). It can be done in one of the following three ways; The tension in the strings will be : (A) the same in all cases (B) least in (i) (C) least in (ii) (D) least in (iii) 7. A rod of length l and negligible mass is suspended at its two ends by two wires of steel (wire A ) and aluminium (wire B ) of equal length. The crosssectional areas of wires A and B are 1.0 mm2 and 2.0 mm2 , respectively. (YAl = 70 × 109Nm−2 and Ysteel = 200 × 109Nm−2 ) (A) Mass m should be suspended close to wire A to have equal stresses in both the wires (B) Mass m should be suspended close to wire B to have equal stresses in both the wires (C) Mass m should be suspended at the middle of the wires to have equal stresses in both the wires (D) Mass m should be suspended close to wire A
to have greater stress in wire B 8. When a stone is suspended by a wire, the extension of the wire is l. When the wire is rotated by holding the top end, it traces a conical pendulum of semi vertical angle θ. The extension of the wire is : (Neglect the mass of wire) (A) l cos θ (B) lcos θ (C) lsin θ (D) l sin θ 9. Three spheres A, B and C having radii R, 2R and 3R respectively are coated with carbon black on their outer surface. The wavelengths corresponding to maximum intensity are 3000Å, 4000Å, 5000Å respectively. The power radiated by them are QA,QB and QC. (A) QA is maximum (B) QB is maximum (C) QC is minimum (D) QA = QB = QC 10. The pressure that has to be applied to the ends of a steel wire of length 10 cm to keep its length constant when its temperature is raised by 100∘C is (For steel Young's modulus is 2 × 1011Nm−2 and coefficient of thermal expansion is 1.1 × 10−5 K −1 ) (If the deformation is small, then the stress in a body is directly proportional to the corresponding strain.) (A) 2.2 × 108 Pa (B) 2.2 × 109 Pa (C) 2.2 × 107 Pa (D) 2.2 × 106 Pa 11. A heating curve has been plotted for a solid object as shown in the figure. If the mass of the object is 200 g, then latent heat of vaporization for the material of the object, is : [Power supplied to the object is constant and equal to 1 kW ] (A) 4.5 × 106 J/kg (B) 4.5 × 106 cal/kg (C) 4.5 × 104 J/kg (D) 4.5 × 104 cal/kg 12. For an ideal liquid : (A) the bulk modulus is infinite (B) the bulk modulus is zero (C) the shear modulus is infinite (D) the shear modulus is zero 13. A copper and a steel wire of the same diameter are connected end to end. A deforming force F is applied to this composite wire which causes a total elongation of 1 cm. The two wires will have. (YCu ≠ YSt). (A) the same stress (B) different stress (C) the same strain. (D) different strain 14. Three rods of copper, brass and steel are welded together to form a Y-shaped structure. Area of cross-section of each rod = 4 cm2 . End of copper rod is maintained at 100∘C whereas ends of brass and steel are kept at 0 ∘C. Lengths of the copper, brass and steel rods are 46,13 and 12 cm, respectively. Thermal conductivities of copper, brass and steel are 0.92,0.26 and 0.12 CGS units, respectively. Rate of heat flow through copper rod is : (A) 1.2cal/s (B) 2.4cal/s (C) 4.8cal/s (D) 6.0cal/s REASONING TYPE FOR QUESTION 15 - 16 (A) Statement-1 is True, Statement-2 is True and Statement-2 is a correct explanation for Statement-1 (B) Statement-1 is True, Statement-2 is True and Statement-2 is NOT a correct explanation for Statement-1 (C) Statement-1 is True, Statement-2 is False (D) Statement-1 is False, Statement-2 is True
15. Statement 1 : Two rods A and B of different material but of the same length and equal areas of cross-section are held fixed at both ends as shown. If a force is now applied, the energy densities are the same. Statement 2 : The strains in the two materials are the same. 16. Statement 1 : Water is filled up in a hollow cylinder container of conducting bases and adiabatic curved surface and kept vertical in an isolated system. If temperature of cylinder is decreased slowly from the bottom. The ice formation will start from the bottom. Statement 2 : The temperature of liquid which is at the top will be lowest first. PARAGRAPH FOR QUESTIONS 17 - 19 A rod of length l, cross section area A, mass m and Young's modulus Y is suspended vertically. It has some elongation. The rod is now pivoted at one end so that it is horizontal. Then it is rotated uniformly in the horizontal plane about the vertical axis through the pivot. It has the same elongation. 17. When suspended vertically, the elongation in the top half is : (A) mgl 8AY (B) mgl 4AY (C) 3mgl 8AY (D) mgl 2AY 18. If the rod is rotated with angular velocity ω, the tension at the pivot is : (A) m 2 ω 2l (B) m 2 ω 2lg (C) m 3 ω 2l (D) mω 2l 19. In the above case value of ω to produce the same extension as in the first case in which the rod is suspended vertically is : (A) √ g l (B) √ g 2l (C) √ 3g l (D) √ 3g 2l 20. A uniform cylinder of length L and mass M having cross-section area A is suspended with its length vertical from a fixed point by a massless spring such that it is half submerged in a liquid of density σ at equilibrium position. The extension x0 of the spring when it is in equilibrium, is : (A) Mg k (B) Mg k (1 − LAσ M ) (C) Mg k (1 − LAσ 2M ) (D) Mg k (1 + LAσ M ) 21. If a piece of metal is heated to temperatures and then allowed to cool in a room which is at temperature θ0, the graph between the temperature T of the metal and time t will be closed to : (A) (B) (C)