PHYSICS MECHANICS Past Paper PDF 2038

AF-5485 B.Sc. Part–I (Semester–I) (CBCS) (New) Examination a il PHYSICS E m Mechanics, Properties of Mater Oscillation & Relativity G...

AF-5485 B.Sc. Part–I (Semester–I) (CBCS) (New) Examination a il PHYSICS E m Mechanics, Properties of Mater Oscillation & Relativity G l Time : Three Hours] [Maximum Marks : 80 ai R E Em Note :— (1) All questions are compulsory. A R (2) Draw suitable and neat diagram wherever necessary. EG 1. Choose the correct alternative : R (i) The SI unit of torque is _____. AR (a) N-m (b) N/m (c) Nm2 (d) N2/m (ii) Radius of gyration of body depends on _____. (a) Mass and size of body (b) Size of body (c) Mass of body (d) Mass distribution about axis of rotation rev (iii) The angular speed of a flywheel making 120 min a il is _____ rad/sec. (a)  E (b) m 2 (c) 4 2 E G (d) 4 R (iv) What remains constant when the earth revolves around the sun ? R (a) (c) Angular momentum A Linear kinetic energy (b) (d) Linear momentum Angular kinetic energy (v) In compound pendulum, centre of suspension and centre of oscillations are _____. (a) Not interchangeable (b) Interchangeable (c) At equal distance from C.G. (d) None of the above (vi) The velocity of a particle performing SHM, when it passes through its mean position is _____. (a) Maximum (b) Minimum (c) Intensity (d) Zero (vii) A system exhibiting SHM must possess : (a) Inertia only a il a il (b) Elasticity only (c) E m Elasticity, inertia and an external force E m E G (d) Elasticity as well as inertia E G R R R (viii) A simple pendulum is taken from the equator to the pole, its period _____.R A (a) Decreases (b) Increases A (c) Remain the same (d) Decreases and then increases LV–21252 1 (Contd.)  (ix) According to Newton's formula, the velocity of sound in air is _____ m/s. (a) 280 (b) 332 (c) 331.6 (d) 350 (x) a il The relation between velocity, frequency 'f' and wavelength ''of a wave ' ' is equal to _____. m GE (a) /f (b) f/ l (c) f (d) + f ai RE Em (xi) Ultrasonic waves can be transmitted over a long distances without any appreciable loss of AR energy because of their ______. EG (a) Small wavelength (b) Large wavelength (c) Medium wavelength (d) None of the above R (xii) In stationary wave, the distance between two successive nodes or two successive antinodes is AR equal to ______. (a)  (b) /2 (c) /3 (d) /4 (xiii) The dimensional formula for shear strain is ______. (a) [M0L1T1] (b) [M2L0T2] (c) [M0L0T0] (d) il None of above a (a) Increases (b) m (xiv) According to Hook's law, if stress is increased, the ratio of stress to strain ______. E Decreases (c) Becomes zero E G (d) Remains constant R R (xv) Poisson's ratio can be expressed as : (a) A Longitudinal strain / Lateral strain (b) Lateral strain / Longitudinal strain (c) Longitudinal strain × Lateral strain (d) None of the above (xvi) Bulk modulus of a material is related to change in ______. (a) Length (b) Shape (c) Volume (d) All of these (xvii) "Every planet revolves in an elliptical orbit round the sun with sun at one of its foci" is the statement of ______. (a) a il Kepler's law of elliptical orbit (b) Kepler's law of mass a il m m GE E (c) Kepler's law of period (d) Newton's gravitation law E (xviii)Length contraction happens only when ______. E G (a) R In perpendicular direction to the direction of motion R R R A (b) Along the direction of motion (c) Both (a) and (b) A (d) None of the above LV–21252 2 (Contd.)  (xix) Newton's law of gravitations applies to ______. (a) Small bodies only (b) Planets only (c) Both small and big bodies (d) None of above a il (xx) The dimensional formula for gravitational constant is ______. (a) [M–1L3T–2] E m (b) [M1L–3T–2] (c) G [M3L–1T–2] (d) [M–2L1T–3] 1×20=20 l ai 2. R E (A) Answer the following questions (any two) : Em A R (i) Define Angular momentum. State its SI unit and dimensions. EG (ii) Derive an expression for moment of inertia of thin uniform disc about its diameter. (iii) What is meant by gyroscope ? State the uses of gyroscope. R (iv) A cylinder of radius 20 cm is rolling along the surface with constant speed of 80 cm/s. AR What is the rotational speed of the cylinder about its axis ? 2×2=4 (B) Answer the following questions (any two) : (i) State and prove the principal of conservation of angular momentum. (ii) Obtain an expression for moment of inertia of solid cylinder about an axis thruogh its centre and perpendicular to its axis of cylindrical symmetry. (iii) What is meant by moment of inertia of a rigid body ? Write its SI Unit and dimensions. a il Write a note on physical significance of moment of inertia. E m (iv) A flywheel of mass 500 Kg , radius 1 m makes 500 rev. Assuming the mass to be E G min 3. R R concentrated along the rim. calculate the energy of the flywheel. (A) Answer the following questions (any two) : 4×2=8 (i) A Define compound pendulum and bifilar oscillations. (ii) Derive the differential equation of linear SHM. (iii) A simple harmonic motion is represented by y = 5 sin (20t + 0.5). What is its amplitude, angular frequency, frequency and phase ? Displacement is measured in metre and time in second. (iv) Show that length of second's pendulum is approximately 1 m. 2×2=4 (B) Answer the following questions (any two) : (i) Show that simple pendulum performs linear SHM and hence obtain an expresion for its periodic time. (ii) a il Derive the equation for periodic time of torsional pendulum. a il m m (iii) Solve the differential equation of SHM to obtain expression for displacement of a particle E E G performing SHM. E E G RR RR (iv) Derive the equation for periodic time of compound pendulum. 4×2=8 4. (A) Answer the following questions (any two) : A (i) Define : A (1) Transverse wave (2) Longitudinal wave. LV–21252 3 (Contd.)  (ii) Explain the term : Overtones. (iii) State the any two properties of ultrasonic waves. (iv) What is Lissajous figures ? 2×2=4 a il (B) Answer the following questions (any two) : (i) E m Explain in detail the production of ultrasonic waves by piezoelectric effect. G l ai (ii) R E Obtain an expression for velocity of transverse wave on stretched string. Em (iii) Obtain an expression for velocity of sound wave in air with the help of necessary diagram. A R(iv) What is standing waves ? State the characteristics of it. 4×2=8 EG 5. (A) Answer the following questions (any two) : (i) Define : R AR (a) Young's modulus (b) Bulk modulus. (ii) What is angle of twist and angle of shear ? (iii) What is Poisson's ratio ? What is its SI Unit ? (iv) Distinguish between elasticity and plasticity. 2×2=4 (B) Answer the following questions (any two) : (i) a il Derive an expression for depression of a beam supported at the ends and loaded at the centre. E m (ii) G Describe Maxwell's needle method for determinataion of modulus of rigidity of the material. E R (iii) Derive an equation for the bending moment of beams having rectangular and circular R cross-sections. A (iv) A cantilever of breadth and depth 0.01 m and 1 m long is clamped horizontally at one end. When a load of 1 kg is applied to the free end the depression of the end is 4 ×10 –2 m. Calculate Young's modulus of the material of cantilever (g = 9.8 m/s2). 4×2=8 6. (A) Answer the following questions (any two) : (i) Define : (a) inertial frame of reference (b) Non-inertial frame of reference. (ii) Show that g = GM R2 a il a il E m E m Where, M – Mass of earth, R – radius of earth, G – Universal gravitational constant and E G 'g' acceleration due to gravity. E G R R (iii) Give the four uses of artificial satellite. R R A A (iv) At what speed does a meter stick move if its length is observed to shrink to 0.5 m ? 2×2=4 LV–21252 4 (Contd.)  (B) Answer the following questions (any two) : (i) Derive the relation E = mc2 (ii) Explain variation in acceleration due to gravity with altitude. a il (iii) What is satellite ? Obtain an expression for speed of revolution of satellite in its orbit at m height 'h' above the earth surface. E G l (iv) A space craft is moving relative to the earth. An observer on the earth finds that between ai R E 1 pm to 2 pm according to his clock and 360/sec. elapse on space craft's clock. What Em A R is the spacecraft speed relative to the earth ? 4×2=8 EG R m a il AR G E R E A R a il a il E m E m E G E G R R R R A A LV–21252 5 25