beatty BTYSS 4E5N ScPhy PRELIM 2020 QP2

SUBJECT : Science Physics LEVEL : Sec 4E/5N PAPER : 5076 / 2 DURATION : 1 hour 15 minutes SETTER : Mrs Seah-Pay Ling Ling DATE : 27 Aug 2020 CLASS : NAME : REG NO : READ THESE INSTRUCTIONS FIRST Write your register number, name and class on the work you hand in. You may use an HB pencil for any diagrams, graphs, tables or rough working. Write in dark blue or black pen. Do not use staples, paper clips, glue or correction fluid. The use of an approved scientific calculator is expected, where appropriate. You may lose marks if you do not show your working or if you do not use appropriate units. Section A Answer all questions. Write your answers in the spaces provided on the Question Paper. Section B Answer any two questions. Write your answers in the spaces provided on the Question Paper. At the end of the examination, fasten all your work securely together. The number of marks is given in brackets [ ] at the end of each question or part-question. _____________________________________________________________________ This paper consists of 18 printed pages (including this cover page) For Examiner’s use Section A /45 Q Q Section B /20 Total /65 BEATTY SECONDARY SCHOOL PRELIMINARY EXAMINATION 2020 [Turn over]

- 2 - Section A (45 Marks) Answer ALL questions in the space provided. Examiner’s Remark 1 A positively-charged metal sphere P is hung from an insulating string as shown in Fig. 1.1. Fig. 1.2 shows the effect on P when a negatively -charged metal sphere Q on an insulated rod is positioned cl ose to it. The string makes an angle  with the vertical. Given that the mass of sphere P is 5.0 x 10 -3 kg and the attraction force acting on P is 1.5 x 10-1 N. Draw a labeled vector diagram to determine the tension of the string and the angle  made by the string with the vertical. scale = ………………………..…….. tension of string = ……………….. N angle,  = .………………..  [4] Insulating rod Fig. 1.1 P Fig. 1.2 P Q

- 3 - 2 Fig. 2.1 shows the speed-time graph of a car and a lorry travelling on a straight road. The lorry is travelling at a uniform speed of 15.0 m/s. The car is travelling at 10 m/s. It then accelerates uniformly from t = 5.0 s to t = 12.0 s, and continues the rest of the journey with a uniform speed of 18.0 m/s. Examiner’s Remark (a) Calculate the acceleration of the car between t = 5.0 s to t = 12.0 s. acceleration = ……………….. m/s2 [2] (b) Calculate the average speed of the car from t = 0 s to t = 18.0 s. speed = ……………….. m/s [2] (c) State how the distance between the car and the lorry changes during the period of (i) t = 5.0 s to t = 9.4 s ………………………………………………………………………………… ………………………………………………………………………………… [1] (ii) t = 9.4 s to t = 12.0 s ………………………………………………………………………………… ………………………………………………………………………………… [1] Fig. 2.1

- 4 - 3 Fig. 3.1 below shows part of a boiler in a steam engin e. Steam escapes through the valve when the pressure inside the boiler becomes too high. Examiner’s Remark (a) Explain how heat is transferred to the water through the steel body. ………………………………………………………………………………… ………………………………………………………………………………… ………………………………………………………………………………… ………………………………………………………………………………… [2] (b) When the pressure inside the boiler reaches 4.0 x 10 5 Pa, the valve opens. The area of the va lve in contact with the steam is 2.0 x 10–4 m2. (i) Calculate the upward force exerted on the valve for it to open. upward force = ……………….. N [2] mass M handle pivot valve water heat steel body 50 cm 30 cm Fig. 3.1

- 5 - (ii) The mass of the handle is 1.25 kg. Calculate the weight of the handle given that gravitational field strength is 10 N/kg. Examiner’s Remark weight = ……………….. N [1] (iii) Given that the handle is 1 m long, calculate the maximum value of mass M such that the valve will open when the pressure inside the boiler is 4.0 x 105 Pa. mass, M = ……………….. kg [2] 4 Explain the following observations using the kinetic theory of matter. (a) Fig.4.1 shows a beaker of alcohol that is placed on a puddle of water. Air is bubbled into the beaker. The alcohol evaporates quickly and the water on the table freezes into ice. Describe how the evaporation of the alcohol causes a cooling effect on the water. ………………………………………………………………………………… ………………………………………………………………………………… ………………………………………………………………………………… [2] Fig. 4.1 Air is bubbled into beaker Water freezes into ice alcohol Air is bubbled into beaker Water freezes into ice

- 6 - (b) During freezing, the temperature of water remains constant although heat is being removed. Examiner’s Remark ………………………………………………………………………………… ………………………………………………………………………………… ………………………………………………………………………………… ………………………………………………………………………………… [2] 5 A microwave oven uses micr owaves to heat food. The common frequency used is roughly 2500 MHz. Microwaves in this frequency range have the following properties:  They are absorbed by water, fats and sugars and converted directly into atomic motion.  They are not absorbed by most plastics, glass or ceramics.  They are reflected by metals, which is why metal pans do not work well in a microwave oven. (a) Calculate the wavelength of the microwave used in the microwave oven. wavelength = ……………….. m [2] (b) State one use of microwave in the communication field. ………………………………………………………………………………… [1] (c) State one other difference between the microwaves and ultrasound wave, without the comparison of their wavelengths and frequencies. ………………………………………………………………………………… ………………………………………………………………………………… [1]

- 7 - 6 A clarinet contains a thin strip of material, known as the reed. A musical note is produced when the reed vibrates, causing molecules in the air nearby to vibrate at the same frequency. Fig. 6.1 shows the clarinetist and audience in a concert room. Examiner’s Remark A sound is heard by a listener , X, who is 21 m from the clarinet. The clarinet is making a note of frequency 220 Hz. (a) Given that the speed of sound in air is 330 m/s, calculate how many vibrations the reed makes before the sound reaches the listener X. number of vibration = ……………….. [3] Fig. 6.1 X Y wall

- 8 - (b) Another listener Y is further away from the clarinet as shown in Fig. 6.1. Fig. 6.2 shows the pressure-time graph of a particle as the sound wave passes from clarinet to listener X. Sketch on Fig. 6.2, the pressure -time graph of a particle as the sound wave passes from the clarinet to listener Y, which is heard as softer and of the same pitch as compared to listener X. Examiner’s Remark Fig. 6.2 [2] 7 (a) A light metallic coated sphere P is suspended by an insula ting string. Sphere P is in contact with an uncharged metal sphere A which i s fixed on an insulating stand. A highly positively charged sphere B is moved tow ards sphere A as shown in Fig. 7.1.