2 Section A Answer All The Questions In This Section.

2 Section A

For Examiner’s Use

Answer all the questions in this section. 1

Fig. 1.1a shows a series of eight electronic timers, positioned at an equal interval of 20 m from each other along a straight road. A car, starting from rest, is driven along the road. All timers are started the moment the car starts moving, and each timer is stopped when the front of the car passes it. electronic timer A B C D E F Fig. 1.1a

time (s) 4.3 6.0 7.4 8.5 9.5 10.5

Fig. 1.1b

Fig. 1.1b shows the data collected from timers A to F. (a) The car is undergoing uniform acceleration for the first 100 m. (i) Define what is meant by uniform acceleration. …...………………………………………………………………………………….. …………………………………………………………………………………….[1] (ii) Explain how the results show that the car is accelerating in the first 100 m. ….………………………………………………………………………………….. …………………………………………………………………………………….. ….………………………………………………………………………………….. ………………………………………………………………………………….[2] (b)

Calculate the average speed of the car in the first 100 m.

average speed = ………………………[2] (c)

The car moves at a constant speed once it passes 100 m. Deduce the time recorded by timer G and timer H. timer G = ………………………

timer H = …………………..[1]

3 2

Fig. 2.1 shows a remote control toy helicopter of mass 1.5 kg rising upwards at a constant acceleration of 2.0 m/s2. Take g = 10 N/kg.

For Examiner’s Use

Fig. 2.1 (a) On Fig. 2.1, draw all the forces acting on the toy helicopter.

[2]

(b) Calculate the force generated by the propeller.

force generated by propeller = ………………………[2] (c) When the toy helicopter reaches at height of 10 m, it hovers at this elevation. (i) What can you say about the forces acting on the toy helicopter at this moment? ……..………………………………………………………………………………….. ……...……………………………………………………………………………….[1] (ii) At the height, the propeller suddenly stops turning. Using the principle of conservation of energy, find the speed at which the helicopter is falling when it is 5 m above the ground.

speed = ………………………[3]

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4 For

3

Fig. 3.1 shows a cat in a diving bell of volume 12 m3. As the bell is lowered into the Examiner’s water, the water level rises to fill 1 m of the bell. The temperature of the air remains Use constant. Take g= 10 N/kg and density of water is 1000 kg/m3. atmospheric pressure (100 000 Pa)

1m Fig. 3.1 (a) Explain, in terms of the molecules of air, why the pressure inside the diving bell increases as it is being lowered. …………..………………………………………………………………………………….. …………………………………..………………………………………………………….. ………….………………………………………………………………………………….. …………...……………………………………………………………………………….[2] (b) Determine the pressure in the diving bell when the diving bell is filled with 1 m of water.

pressure = …………………………[2] (c) Calculate the volume of the diving bell when it is under water. State the formula that you use in your calculation.

volume = …………………………[2]

5 4

Fig. 4.1 shows two incident rays of light on the top facets of a diamond and a glass respectively.

For Examiner’s Use

top facets

bottom facets Fig. 4.1

Diamond has a refractive index of 2.4 and glass has a refractive index of 1.5. (a) Determine the critical angle for diamond.

critical angle of diamond = ………………[2] (b) Given that the critical angle of glass is 41.8°, complete the path of light ray in each of the materials shown in Fig. 4.1 as they leave the facets, explain which material, diamond or glass, gives more glitter. ................................................................................................................................. ...…………………………………………………………………………………….…….. ................................................................................................................................. ...…………………………………………………………………………………….…….. ……………….…………………………………………………………………………….. ……………………………..……………………………………………………………[3] (c) Determine the speed of light in the diamond.

speed = ………………[2] [Turn Over

6 5

The spraying of pesticides with crop sprayers makes use of electrostatic principles. A spray gun charges the tiny droplets of pesticide as they leave the nozzle as shown in Fig. 5.1. spray guns

Fig. 5.1 Fig. 5.1 (a) In terms of electron transfer, explain how does the spray gun make the droplets of pesticides positively charged? ................................................................................................................................. ................................................................................................................................. …..………………………………………………………………………………………[2] (b) Explain why the droplets of pesticides must be charged for this task. ................................................................................................................................. ................................................................................................................................. …..………………………………………………………………………………………[2] (c) Small amount of electric charges can move about in the plants. What type of charges will be attracted to the surface of the leaves by the positively charged drops? Show the distribution of charges in Fig. 5.2. + + leaf

+

Fig. 5.2 Type of charges attracted to the surface: …………………………………………[2]

For Examiner’s Use

7 6

Fig. 6.1 shows a cell of e.m.f. 12.0 V is connected in series with a 250 Ω resistor and a thermistor. The graph on the right shows how the current reading on the ammeter of the thermistor varies with temperature.

For Examiner’s Use

current/ mA

1.00 0.80 0.60 Fig. 6.1 0.40 0.20 0.00 0

20

40

60

80

100

temperature / °C

(a) State the current reading at the lower fixed point and the upper fixed point. current reading at lower fixed point = ……………………… current reading at upper fixed point= ……………………….

[1]

(b) Determine the resistance of the thermistor at 80 °C.

resistance = ………………[2] (c) Explain how the voltmeter reading will change as the temperature drops from 100 °C to 0 °C. ……………………………………………………………………………………………….. ……………………………………………………………………………………………….. ……………………………………………………………………………………………….. ………………………………………………………………………………………..…...[2] [Turn Over

8 7

Double insulation and earth wires protect the user of the electrical appliance. Circuit breakers and fuses are safety features installed in our homes to protect the electrical appliance. (a) Explain how the double insulation protects the user of electrical appliance. ………………………………………………………………...…………………………… ………………………………………………………………...…………………………… ………………………………………………………………...…………………………… ……..…………………………………………………………...…………………..…...[2] (b) Fig. 7.1 shows the inside of a circuit breaker under normal conditions.

Using Fig. 7.1, explain what happens when there is a sudden surge in current. ………………………………………………………………...…………………………… ………………………………………………………………...…………………………… ………………………………………………………………...…………………………… ………………………………………………………………...…………………………… ………………...………………………………………………...…………………..…..[2]

For Examiner’s Use

9 8

A student sets up a simple apparatus to study the current flowing from terminal X to Y through a solenoid as shown in Fig. 8.1.

For Examiner’s Use

pivot pointer S

scale

N X Y Fig. 8.1 (a) The student claims that this apparatus can be used to measure magnitude of direct current when it is connected across XY. Explain how this works. ………………………………………………………………………………………………. ………………………………………………………………………………………………. ………………………………………………………………………………………………. ………………………………………………………………………………………………. ………………………………………………………………………………………..…..[3] (b) Suggest 2 ways to increase the sensitivity of this set up. 1 ……………………………………………………………………………………..…….. 2 ……………………………………………………………………………………..…...[2] (c) Another student connects a centre-zero galvanometer across XY. He then uses a spring and sets magnet vibrating up and down vertically. Describe and explain what is likely to be observed on the galvanometer. ………………………………………………………………………………………………... ………………………………………………………………………………………………... ………………………………………………………………………………………………... ………………………………………………………………………………………………... ……………………………………………………………………………………………..[3]

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10 Section C (30 marks) Answer all the questions in from this section. Question 11 has a choice of parts to answer. 9

Fig. 9.1 shows a thermocouple thermometer. Junction A of the thermocouple is in melting ice. wire Q

wire P

junction A beaker of melting ice

junction B

Fig. 9.1 (a) Suggest suitable metals for the wire P and wire Q. wire P = ………………………

wire Q = ……………………….... [1]

(b) What would be the millivoltmeter reading when junction B is placed in another beaker containing melting ice? Give a reason for your answer. ……………………………………………………………………………………………... ……………………………………………………………………………………………... ……………………………………………………………………………………………... …………………………………………………………………………………………..[2] (c) When junction B is placed in steam of a boiling water, the millivoltmeter reading reads 25 mV. What is the temperature of the junction B when the millivoltmeter reads 7.5 mV?

temperature =…………............[2] (d) State two key advantages of using thermocouple thermometer. ……………………………………………………………………………………………... ……………………………………………………………………………………………... ……………………………………………………………………………………………... …………………………………………………………………………………………..[2]

For Examiner’s Use

11

(e) A heater which supplies thermal energy of 1.2 kJ every second is completely immersed in the beaker of melting ice at 0 °C. The beaker contains 150 g of ice and 250 g of water. Calculate the amount of time required to raise the temperature of the beaker and its content to room temperature of 30 °C. You may make use of the following information: • Specific heat capacity of water is 4 200 J/(kg°C) • Specific heat capacity of ice is 2 100 J/(kg°C) • Heat capacity of beaker is 67 J/°C • Specific latent heat fusion of water is 3.36 x 105 J/kg • Specific latent heat vaporisation of water is 2.26 x 106 J/kg

time taken =…………[3]

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For Examiner’s Use

12 10

During the construction of a tunnel for MRT, an engineer faces the challenge of the need to locate the position of possible hard rocks in water. In water He employs echolocation method where a pulse of ultrasound from the ship is reflected by the hard rock as shown in Fig. 10.1. ultrasound emitter and sensor water surface

hard rock Fig. 10.1 (a) What is meant by ultrasound? ……….………………………………………………………………………………….. ………...………………………………………………………………………………[1] (b) Describe how the vibrations of the emitter produces waves of ultrasound and suggest how these waves are subsequently detected by the sensor. ………………………………………………………………………………………………... ………………………………………………………………………………………………... ………………………………………………………………………………………………... ………………………………………………………………………………………………... ………………………………………………………………………………………………... ………………………………………………………………………………………………... ……………………………………………………………………………………………..[3]

For Examiner’s Use

13 For Examiner’s Use

(c) The wavelength of the ultrasound is 0.03 m and its speed in water is 1 500 m/s. Calculate the frequency of this ultrasound.

frequency = ……………………[2] (d) Fig. 10.3 shows the trace on the screen of a cathode –ray oscilloscope (c.r.o.) of the transmitted and the reflected pulse. The time base setting on the c.r.o. is 20 ms/cm.

1cm

Fig. 10.3 Determine the depth of the hard rock in water.

depth = ……………………[2] (e) Describe one other application of the ultrasound. ……………………………………………………………………………………………. …..………………………………………………………………………………………... …………………………………………………………………………………………... …………………………………………………………………………………………... …………………………………………………………………………………………..[2] [Turn Over

14 For Examiner’s Use

11 EITHER Lasik (laser-assisted in situ keratomileusis) has become a popular refractive surgery for correcting myopia commonly known as short-sightedness for many teenagers and young adults. Many patients choose Lasik as an alternative to wearing corrective eyeglasses or contact lenses. The surgery involves the use of laser (light amplification by stimulated emission of radiation) to permanently remove some of the corneal tissue and thereby changing the shape of the cornea. The technology has advanced such that now it requires less time for the patient's recovery, and the patient feels less pain overall. Fig. 11.1 shows the information about the wavelength and the output power of some types of laser. types of laser wavelength /m output power /W -7 Excimer 1.93 x 10 20.0 Argon 4.98 x 10-7 2.0 Krypton 5.68 x 10-7 0.5 -7 HeNe 6.33 x x 10 0.005 Yag 10.6 x 10-7 50.0 Fig. 11.1 The visible spectrum has wavelengths ranging from 4.0 x 10-7 m to 7.0 x 10-7 m. (a)

Which laser emits ultraviolet radiation? ……………………………………………………………………………………………....[1]

(b)

Describe the medical uses of ultraviolet radiation. …………………………………………………………………………………………………. …….....………………………………………………………………………………………... …………………………………………………………………………………………………. …….....………………………………………………………………………………………... ………………………………………………………………………………………….......[2]

(c)

Calculate the frequency of light from the HeNe laser. State clearly any constant used.

frequency = ……………………[2]

15 (d)

During a lasik treatment, light from the Excimer laser is used to treat a patient’s eye. This laser fires 15 short pusles of light. Each pulse lasts 0.5s. Calculate the energy given out by the laser during the treatment.

energy = ……………………[2] (e)

Despite this advancement in technology, not all short-sighted patients can undergo lasik treatment. They still need to rely on the traditional diverging lens to help them to see far objects. Fig. 11.2a shows the condition of short-sightedness where the image formed is in front of the retina.

converging lens

retina

Fig. 11.2a

diverging lens

Fig. 11.2b

On Fig. 11.2b, complete the light path to show how the use of a diverging lens can help to allow a distant object to get focus on the retina. Explain how the diverging lens achieve this. …………………………………………………………………………………………………….. …….....………………………………………………………………………………………........ …………………………………………………………………………………………………….. …….....………………………………………………………………………………………........ …………………………………………………………………………………………............[2] (f)

Describe the image formed on the retina. …………………………………………………………………………………………............[1]

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16 OR Fig. 11.3a shows a newspaper cutting from Straits Time on 15 Jul 2009 of a newly installed off-shore wind farm. The world has seen a rise in the number of off-shore wind farms as the wind is more reliable at sea. Fig. 11.3b shows a simple setup to illustrate how wind power can be used to generate electricity.

Wind farm gets 5-MW turbine

Following a one-year delay, the 5-MW turbine was installed 45 kilometres north of the island of Borkum, Germany. -- PHOTO: AFP

Fig. 11.3a (a)

Fig. 11.3b

Explain the term 5 MW. ……………………………………………………………………………………………......... ……………………………………………………………………………………………....[1]

(b)

Explain the term how the electricity can be generated when the blades turn. ………………………………………………………………………………………………….. …….....……………………………………………………………………………………….... ………………………………………………………………………………………………….. …….....………………………………………………………………………………………[2]

17 (c)

State the purpose of the iron rod. ……………………………………………………………………………………………......... ……………………………………………………………………………………...………....[1]

(d)

State one advantage of a rotating magnet over a rotating coil generator. ……………………………………………………………………………………………......... ………………………………………………………………………………………...……....[1]

(e)

A transformer is used to step up the voltage from 50 kV to 300 kV. (i)

Determine the turn ratio for this transformer.

turn ratio=………………..[2] (ii)

Assuming that this transformer is 100% efficient, calculate the current in the secondary coil.

current=………………..[2] (iii)

In practice, the transformer is hardly 100% efficient. Suggest a possible reason for this. …………………………………………………………………………………………… …...…………………………………………………………………………………....[1]