COLLEGE OF ENGINEERING PUTRAJAYA CAMPUS FINAL EXAMINATION TRIMESTER 1, 2010/2011

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1 COLLEGE OF ENGINEERING PUTRAJAYA CAMPUS FINAL EXAMINATION TRIMESTER 1, 2010/2011 PROGRAMME SUBJECT CODE : Foundation in Engineering : PHYF144 SUBJECT : Physics 3 DATE : October 2010 TIME VENUE : 2 hours 30 minutes : Library Exam Hall INSTRUCTIONS TO CANDIDATES: 1. This paper consists of TEN (10) questions in Part A and FIVE (5) questions in Part B in FIVE (5) pages. 2. Answer ALL questions in Part A and ANY 4 questions in Part B. 3. Write ALL answers in the answer booklet provided. 4. Write answer to each question in Part B on a new page. THIS QUESTION PAPER CONSISTS OF 6 PRINTED PAGES INCLUDING THIS COVER PAGE. Page 1 of 7

2 Constants: Acceleration due to gravity = 9.80 m/s 2 ; volume expansion coefficient of water = /K; density of water at 60.0 C = g/ml; speed of light in vacuum m/s ; Planck constant = Js; Rydberg s constant = m -1 ; mass of electron = kg; n air = 1.00; n oil = 1.48; n water = 1.33; 1 liter = 10 3 m 3 ; 1 atm = Pa; 1 ev = J Part A: Answer ALL questions. Each question is worth 2 marks. 1. The Antarctic has the coldest temperature on the earth with a coldest reported temperature of 129 F. Express this temperature in Kelvin scale. [184 K] 2. A Styrofoam box with cover is used to keep drinks cold at a picnic in a summer. Is heat flowing in or out of the Styrofoam box? When the day turns cloudy, does the rate of heat transfer through the box by conduction increase, decrease, or remain the same? [flows in; decreases] 3. A simple pendulum is 5.00 m long. What is the period of this pendulum if it is placed in a truck that is accelerating down a slope (30.0 below horizontal) at 2.00 m/s 2? [4.69 s] 4. A transverse sinusoidal wave with angular frequency 200 rad/s travels along x axis in a taut string. Figure 1 shows the snap shot of the wave at time t = 0 with a particle P on string travelling downward. Write the wave function for the wave. [y = (6.00 cm) sin (10 x t)] y (cm) 20.0 cm 6.00 P x (cm) Figure 1 Page 2 of 7

3 5. Consider a pair of speakers in a radio driven by the same oscillator. The sound waves from the each speaker have the same frequency and amplitude. Can fully destructive interference happen in front of the speakers? State the reason why. [Yes. Whenever the path difference is (n+ ½) or the phase difference is (2n+1), where n = 0, 1, 2,...] 6. A taut string of density 15.0 g/m is under a tension of 80.0 N. How much energy is transmitted per second down the string vibrating at a frequency of 60.0 Hz and amplitude of 6.00 cm? [280 W] 7. A stretched string of certain length is observed to vibrate in four equal segments. The displacement of standing wave formed in the string is described by y ( 2.80 cm) sin( 3 x)cos(120 t) where x and y are in centimetres and t is in seconds. Determine the length of the string. [4/3 m] 8. In a Young s double-slit experiment, interference does happen too at any locations between the bright fringe and the adjacent dark fringe. What is the phase difference between the interfering waves at the midpoint between the central bright fringe the adjacent dark fringe? [ /2] 9. Two radio antennas separated by 10.0 m radiate in phase with each other at frequency 35.8 MHz. In what directions (measured from the midpoint of the two antennas) is the intensity maximum? [0, ±56.9 ] 10. Determine the wavelength emitted by hydrogen atom as its electron makes a transition from 2 nd excited state to the ground state. [122 nm] Page 3 of 7

4 Part B: Answer ANY 4 questions. Each question is worth 10 marks. QUESTION 1 (a) It is observed that 60.0 ml of water at 25.0 C completely fills a container to the brim. When the container and the water are heated to 60.0 C, g of water overflows. What is the coefficient of volume expansion of the container? [40.5E-6 /K] [5 marks] (b) One mole of ideal gas with specific ratio of 1.67, originally at a pressure of 200 kpa, undergoes a three-step process. Firstly, it is expanded isothermally from 5.00 L to 10.0 L. It is then compressed isobarically. Finally, it returns to its original pressure and volume adiabatically. (i) Sketch the pv diagram. [1 mark] (ii) Find the volume at the end of isobaric process. [7.57 L] [4 marks] QUESTION 2 (a) The four tires of an automobile are inflated to a gauge pressure of 260 kpa. Each tire has an area of m 2 in contact with the ground. Determine the weight of the automobile. [19.8 kn] [2 marks] (b) (i) Write the Bernoulli equation and describe all the quantities in the equation. (ii) Water enters a house at a speed of 1.20 m/s through 4.00-cm-diameter pipe in the basement under an absolute pressure of 3.00 atm. In a 2.50-cmdiameter pipe on the second floor bathroom 5.00 m above, determine the flow speed and pressure. Assume only the water at the bathroom is turned on and the density of water is 1000 kg/m 3. [3.07 m/s, 250 kpa] [5 marks] Page 4 of 7

5 QUESTION 3 (a) In an experiment to measure the speed of light using the Fizeau s apparatus, the 360-teeth wheel was rotating at 55.0 rad/s. A burst of light passing through a notch was blocked by adjacent tooth on return. If the measured speed was m/s, what was the distance from the wheel to the mirror? [7.54 km] [3 marks] (b) (i) State the Snell s law and describe all the quantities in the law. [2 marks] (ii) A laser beam enters from air a layer of oil resting a glass of water. Is it possibly for total internal reflection to happen at the oil and water interface? If yes, determine the minimum angle (Figure 2). If no, show why it is not possible for total internal reflection to happen? [5 marks] [No. Maximum incident angle = 42.5 < c] Air Oil Water Figure 2 QUESTION 4 (a) When an object is placed 5.00 cm in front of a spherical mirror, the image formed by the mirror is upright and twice the size of the object. What is the radius of curvature of the mirror? [+20 cm] [4 marks] (b) A gold fish is swimming inside a rectangular aquarium. If a child is 5.00 cm from the wall of the aquarium and the index of refraction of water is 1.33, where does the child appear to the fish? [6.65 cm outside the aquarium] Page 5 of 7

6 (c) An ant is 3.00 cm in front of a converging lens with a focal length of 5.00 cm. Construct a ray diagram to locate and describe the image. [7.5 cm in front of the lens; virtual, upright, magnified] QUESTION 5 (a) What is the maximum speed of a photoelectron emitted from a surface whose work function is 5.0 ev when illuminated by a light whose wavelength is 200 nm? [652 km/s] (b) A stopping potential of 3.20 V is needed for radiation whose frequency is Hz. What is the work function (in ev) of the material? [1.77 ev] (c) X-rays of wavelength nm undergo Compton scattering from a target. The scattered rays are detected at 142 relative to the incident rays. (i) Find the wavelength of the scattered x-ray if the ray was scattered by electron; [ nm] (ii) Estimate the wavelength of the scattered x-ray if the ray was scattered by the nucleus of the target. [0.200 nm since 0 for large m] [1 mark] Page 6 of 7

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