University of Lagos Physics SCI-J155 Past Paper PDF 2023/2024

I. UNIVERSITY OF LAGOS. ' -...

I. UNIVERSITY OF LAGOS. ' - SCHOOL OF FOUNDATION STUDIES - ' ~. ' I FIRST SEMESTER EXAMINATION 2023/2024 SESSION \ ltf. --i\.- _ ·:...., ~.... °"ro._,;jg.... ,.ll''.: PHYSICS -SCI-J155 OPTIOND Section A - Multiple Choice Questions Instruction: Answer ALL questions in this Section Time Allowed: 2 hours 1. Parallel light rays propagate across interfaces from one medium to another as shown in the diagram below. What can you infer about the relative sizes of the indices of the respective media. 2. Consider a wave traveling down a cord and the transverse motion of a small piece of the cord. I. \\ihich of the following statement is true? A. The Speed of the wave must be the same as the speed of a small piece of the cord. B. The frequenc.y of the wave must be the same as the frequency of a small of the cord. C. The amplitude of the wave must be srune as the amplitude of a small piece of the cord. D. Both (b) and (c) are true 2 3. A sound wave of amplitude 0.20mm has an intensity of 3.0 \V/m. What will be the intensity of a sound wave of the same frequency when the an1plitude is doubled to 0.40 mm? A. 4.2 W/m2 B. 6.0 W/m2 C. 9.0 W/m2 D. 12 W/m2 4. Given the fundamental mode frequency of a transverse vibration of a stretched wire 1 m long to approximately 250 Hz. If the wire is shortened to 0.4 m at the same tension, the new fundamental frequency of the stretched-wire is A. 102 !-f...z B. 162 Hz C. 312 Hz D. 640 Hz 1 ----- -  ' ' S. Determine the number of wavelengths which is equal to the horizontal diStailCe between Points C and K on the rope in the figure below: A. 1 wavelength B. 2.5 wavelengths C. 3.5 wavelengths D. 4 wavelengths 6. The process in which no heat enters or leav es the system is termed as A. isochoric. B. isobaric. C. adiabatic. D. radiation 7. An object is placed in front of a concave mirr or with a 25.0 cm radius of curvature. An imag e twice the size of the object is fom1ed. At what. distance is the object from the mirror? A. 12.5 cm B.50.0 cm C. 18.75cm D. 25.0 Ctn 8. A boy cannot focus on objects closer to his eyes than 2.5 cm. What refractive power shou ld his corrective lenses have? A. 0.4Dj B. -2.S D C. -36.0 D D. 40.0 D 9. A wav e Vfith amplitude of23.0 c1n appr oaches another wave with amplitude of 11.0 cm. When - the two positive wave pulses constructively interfere with one another, what will be the resulting amplitude of the wave? , __ A. 0.00cm B. 23.0cm C. 12.0cm D. 34.0cm l 0. A helicopter pilot notices waves that strik e a small island arc bending around the back of the island. This property of a wave is called _ __ A. diffraction B. refraction C. interfercnce D. destructive interference \JL) 1. The sound waves of frequency more than 20 KJ-~z ?1"e te~e d as t A. supersonic B. audible C. mfrasomc 0. ultrasonic. '\{,,' 12. Pitch of a note depends u~on:. j- A. frequency B. mtcmnty C. amplitude D. none of the above. 2 --  I 13. A freezer has a Coefficient of performance of 5. If the temperature inside the freezer is 20 °C. What is the temperature at which its rejects heat. {Assume an ideal system) A. 31° C B. 41° C C. 50° C D. 25° C 14. At 40°C, the volume of a gas is 300 ml. The temperature of the gas gets raised to 55°C with no change in pressure. What is the new volume ofthe gas? A. 412.5 ml B. 515.3 ml C. 314.0 ml D. 286.2 ml '\l.,-15. What !s the electrical power which must be supplied to the filament of an electrical bulb 11' operating at 3000 K. The total surface area of the filament is 8 x 10~ (Take e = 0.92) A. 33.8 W B. 40.0 W C. 338 W D. 405 W. 16. The Efficiency of a heat engine may be calculated using _ _ _ _ __ A. QL -1 QH B. QL QH C. 1- QH QL D. w QH 17. The power of a lens can be obtained from the focal point of the same lens using 1 A. p= 1-1 2 B. p= 1 C. p= 1 3 D. p = f- 1 18. A man walks for son1e time with velocity v due east. Then he walks for same time ·with velocity v due north, the average velocity of the man is_ __ B. 2v C. ✓2v D. V E. v/✓2 3 ----  \ \ \ \ ,_ , 35. 1200J of work 1s ·. I d of 250N through a vertical dist;i required by a machine to raise a oa t\_ ---~ 11t Find the efficiency of the machine. A. 62.5% \ B. 70.5% C. 80.5%, D. 69 -5% 36. Water and oil are poured into a tube , open at both ends. They come to the fig. Below. What is the density cquilib~um as sh0Wn. of the oil? Take density of water as lg/ cm Ill. l-i--81>2~ Oil 27.2 T cm J ___ ___ _ b Water A. 1200 kgm - 3 (B) 1650 kgm-· 3 (C) 683 kgm - 3 (D)288 kgrn- 3 37 A geologist finds that a Moon rock whose mass is 9.28 kg has an submerged in water. What is the den apparent mass of 6.18 kg v.ilen sity of the rock? Talce density of wat A. 5600 kgm - 3 er as lg/cm3 (B) 3200 kgm - 3 (C) 2990 kgm - 3 (D) 1435 kgm - 3 38. Two objects of masses m1 and m2 fall from the heights h and h2 magnitude of their momenta when 1 respectively. The ratio of~ they hit the ground is A.~ B ✓~~ C ~~ 39. Assuming you were standing 3m in front of a plain mirror. You top of your head to your waist, Wh can see yourself just from the ere the bottom of the mirror cuts off you wdlk one step towards the mir the rest of your image. If ror what image would be formed. A. You will not be able to see any more of your image. B. Yo u will not be able to see mor e of your image, below your waist. C. You will see less of your image with the cutoff rising to be above you D. No ne of the Above. r waist. 40. Wh en the reflection of an obj ect is seen in a flat mirror, the ima ge exhibits the follo\\rmg properties. A. Real and upright. H. Real and inverted. C. Virtual and upright. D. Virtual and inverted. 6 -- - -- --- --.. - - - - -- - --- --- _j  \ \ \ \ \ ,_ \ Answer any two (2) questions in this subsectio n 5. (a) Differentiate between the following: (i) Thermometric property and thermometric subs tance (ii) heat capacity and specific heat capacity 2mk s each tota l 4mks (b) (i) Explain abnormal behaviour of water as its temperature reduces lmk (ii) Determine the density of 1 mole of oxygen at a pressure of 2.0 x 104 Nm - 2 and temperature of27 3.19 K (R 8.314 J/mo le.K ) 4mks (c) (i) State the first Law of thermodynamics 2mks (ii) Calculate the work done by a gas of 2Jm3 which expand to 4. Jm 3 unde r a constant pressure of 5 Nm - 2. If the te1nperature of the gas is increased such that the new work done 12.1 joules, calculate the final volume occupied is by the gas. 4mks 6. a(i) State five postulates of kinetic theory of matter. Smks (1 mk each) (ii) A helium balloon assumed to be a perfect sphere, has a radius of 18.0 cm. At room temperature,20°c, its internal pressure is 1.0S atm. Find the number of moles of helium in the balloon and the mass of helium needed to infla te the balloon to these values. (R 8.3 l 4J/mole.K) lmk s (b) (i) T\vo bodies are in thermal equilibrium. What does this mean? lmk (ii) If 4000J of heat is applied to a 1.5 kg silve r pendant initially at temperature of 150 ° C. Determine its final temperature (Take specific heat of silver c = 233~ 'kg/K ) 4mks (c) Define the following processes and state their I implication of each on the first law of thermodynamics (i) isothermal process 1 mk \ (ii) isochoric process 1 mk (iv) isobaric process lmk (v) Adiabatic process: 1mk 7. a. (i) State the First law ofthennodynamics 2mk s (ii) Define Brewster's angle? 2mks b. Differentiate with neat sketches and examples, heat engines and heat pump. 4mk s c. Prove that the efficiency of an Otto cycle depe nds only on the compression ratio. 4mks d. Light travelling in water of refractive index nl = 1.33 is incident on a plate of glass of refractive index n2 = 1.53. Calculate the B~ewster's angl e and the angle of refraction? 3mks 10 - ---- ---- - -  8. a. Differentiate between: e waves 2 mar.b L Longitudinal waves and Transvers gnetic waves 2 mark, iL Mechanical waves and Electroma l Qu ality are cha rac teristics of a musical note Name the physica property of b. Loudness, Pitch and teristic depends. 3marla, 1 mk eac h a sowid wave on which each charac 0.002sin(0.5x -62 8t). c. A string wave is described by y = Determine the i. amplitude of the wave ii. frequency of the wave 111. period of the wave 1v. wavelength Smar.ks h, total v. velocity of the wave. 1 mk eac osite ction refl ects at a bar rier and interferes with the incoming wave in opp d. A wave moving in a dire as: the frrst and second waves are given direction. If the displacements of y, =25 sin(l St - 6x) and y 2 =25 sin(15t + 6x) 1.Smarks (i) Find the resulting wave (Y1 + Y2) resulting wave. abo ve y, = 4 cos (2t - 30) and y 2 = -3 sin(2t + 60) then, find the new (ii) jf in d (i) 1.5 marks 11