SMSS MYE 2012 4E Physics P2 QP.docx

7/29/2019 SMSS MYE 2012 4E Physics P2 QP.docx

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Name: ... Reg. No. Class: .

Secondary 4 Express

9

th

May 2012Duration : 1 hour 45 minutesTotal Marks : 80

READ THESE INSTRUCTIONS FIRST

Do not open this Booklet until you are told to do so.

Write your name, register number and class on all the work you hand in.Write in dark blue or black pen.You may use a soft pencil for any diagrams or graphs.Do not use staples, paper clips, highlighters, glue or correction fluid.

Section AAnswerall questions.

Section BAnswerall questions. Question 12 has a choice of parts to answer.

Candidates are reminded that all quantitative answers should include appropriate units.Candidates are advised to show all their working in a clear and orderly manner, as more

marks are awarded for sound use of physics than for correct answers.

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.

Section A

Section B

Total Marks

________________________________________________________________________This question paper consists of19 printed pages

PHYSICS 5058/02

St. Margarets Secondary School

Mid-Year Examinations 2012


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Section A

Answerall the questions in this section.

1 A cable car is ascending along a cable in a skiing resort as shown in Figure 1.1below. At the instant shown, the ends of the cable are making angles of 40 and 10

with the horizontal. Assume that the total mass of the man and the car is 90 kg.

By constructing a suitable vector diagram, find the tensions along the sections ABand BC of the cable. State the scale used.

scale =

tension along AB =

tension along BC = [4]

Figure 1.1


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2 Figure 2.1 shows a martial art expert holding a uniform 10 kg pole of length 2 m.

Determine the vertical forces he must exert with each hand to hold the pole in theposition shown.

force exerted by left hand =

direction =

force exerted by right hand =

direction = [4]


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3 Fig. 3.1 shows the diagram of a piston at two different stages.

(a) Describe the motion of the air molecules in the pump in Figure 3.1.

[2]

(b) Explain in terms of molecular motion why the pressure in Fig. 3.2 should bethree times greater than in Figure 3.1.

[2]

(c) If the piston had been pushed in quickly, the temperature of the air in thepump would have increased.

Explain in terms of molecular motion how this would affect the pressure inthe pump.

[3]

pump issealed Fig. 3.1

Fig. 3.2

2cm 2cm 2cm

Figure 3.1

Figure 3.2


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4 A sonar sends pulse of ultrasound from the bottom of a ship. The reflected pulsesare picked up by a receiver. The speed of ultrasound in water is 1600 m/s.

(a) If the frequency of ultrasound used by the sonar system is 40 kHz, what isthe wavelength of the ultrasound?

wavelength = [2]

(b) If the time interval between sending and receiving a pulse is 0.1 s, what is

the depth of the water below the ship?

depth = [1]

(c) If the frequency of the ultrasound is doubled, what is the effect, if any on the

(i) speed of the ultrasound;

[1]

(ii) wavelength of the ultrasound

[1]


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5 Figure 5.1 represents a ray of light approaching a glass prism along a path parallelto the base of the prism. The refractive index of the glass is 1.52.

(a) Calculate the angle of refraction as the ray enters the prism.

angle of refraction = [1]

(b) Determine the critical angle for the glass.

critical angle = [1]

(c) Complete the path of the light ray on Figure 5.1 through the prism and whenthis ray next meets a glass-air boundary. [3]

Figure 5.1


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6 Figure 6.1 shows a converging lens of a telescope. Light from a point A on a distanthouse is brought to a focus at I.

(a) Complete the rays from A to show how the image at I is formed. [1]

(b) Light from another point B on the same house is brought to a focus at I.Locate the position ofI by completing the ray diagram. [2]

(c) On Figure 6.1, indicate with an f, the focal length of the lens. [1]

Figure 6.1


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Glass rod

Metal can

Galvanometer water tap

Insulating base

G

Fig.8.1Figure 7.1

++++

++

7 Figure 7.1 shows a positively charged glass rod which is lowered into a metal canwhich is connected to a very sensitive galvanometer and then to a water tap.

(a) The galvanometer shows a momentary deflection when the rod is loweredinto the metal can. Explain this phenomenon.

[2]

(b) Explain why the deflection in the galvanometer is only momentary.

[1]

(c) Will the observation be the same if the experiment is carried out with acopper rod instead of the glass rod held by a students hand? Why?

[2]


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8 Figure 8.1 shows a Cathode-ray Oscilloscope (C.R.O.) used to display the voltageacross a variable resistor AB of maximum resistance of 3 . The y-gain control andthe time base of the C.R.O. are set to 2 V/cm and 10 ms/cm respectively. There arethree more resistors, each with a resistance of 3 each in the circuit.

Switch K is now closed and the time base is turned on.

(a) The sliding contact X is moved to B.Calculate the potential difference across resistor AB.

potential difference = [3]

(b) Sketch the trace on the C.R.O. [1]

Figure 8.1

B

A

C.R.O

10 V

K

X

3 3

3

1 cm

1 cm


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(c) If the polarity of the battery is now reversed, sketch the trace on the C.R.O.[1]

(d) The 10 V battery is now replaced by an a.c. supply with peak voltage 10 Vand frequency 25 Hz. Sketch the trace on the C.R.O. [2]

1 cm

1 cm

1 cm

1 cm


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9 Figure 9.1 shows how current I in a diode varies with the potential difference Vacross it.

(a) Describe how I varies with V when

(i) V is negative,

[1]

(ii) V is positive.

[2]

(b) Calculate the resistance of the diode when V is 0.80 V.

resistance = [3]

(c) A student states when V is negative the resistance is zero.State with a reason whether you agree with the student.

[1]

Figure 9.1


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Section B

Answerall the questions from this section.Answer only one of the two alternative questions in Question 12.

10 The Singapore Government has tasked itself with developing green technologies tomeet the goal of making 80 percent of all buildings in the island state green by 2030.The country's first Zero Energy Building was launched as a project to test thewaters. This is also the first such green building in Southeast Asia.

As the Zero Energy Building claim shouts, the 4,500 m2 structure is expected toproduce as much electricity as it uses, besides consuming half less energy than a

non-eco building. Savings-wise, that's S$84,000 a year recouped on electricity.Cost-wise, the Building & Construction Authority (BCA) spent S$11 millionretrofitting this former academy building, which it says cost just 5 percent more thanconventional ones.

Here are some of what's helping to make this a Zero Energy Building:

Solar-Assisted Stack Ventilation System: Solar chimney and ducts pull out hotair, while letting cool air flow in for natural ventilation.

Floor diffusers: These supply cool air which, once warm, will rise to vents in theceiling to be removed.

Greenery system: Roof garden and wall plants help cut heat transmission intothe building.

Photovoltaic technology: Solar panels fitted on the roof, sides, staircase faadeand car park shelter help harvest the sun's rays. BCA claims the 1540 m2 panelscan generate about 207,000 kWh a year, sufficient to power 45 four-room HDBflats over that time frame.

(a) State what is implied by the term Zero Energy Building.

[1]


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(b) Explain the principles behind how the solar chimney and ducts pull out hot airwhile letting cool air flow in using natural ventilation.

[2]

(c) State two ways in which the greenery system (roof garden and wall plants)helps cool the building.

[2]

(d) Assuming the solar panels are 50% efficient, calculate the average amountof solar energy (in kWh) that falls on every square metre of solar panelsevery year.

amount of solar energy = [2]

(e) Hence calculate the average amount of solar energy (in joules) that falls onevery square metre of solar panel every year.

amount of solar energy = [2]

(f) Suggest why it may not be feasible to convert HDB flats to rely mainly onphotovoltaic energy like the Zero Energy Building.

[1]


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11 A carbon thermistor X and a light-dependent resistorY together with two 5.0 kresistors R1and R2 are connected to a 6.0 V battery as shown in Figure 11.1.A lamp is connected across the points A and B.

(a) State the characteristics of

(i) the carbon thermistorX,

[1]

(ii) the light-dependent resistorY.

[1]

(b) (i) If both X andYhave resistance of 5.0 k in darkness, explain whetherthe lamp L is lighted.

[2]

Fig. 11.1

6.0 V

5.0 k

5.0 k

R2

R1 Y

BA

X

L


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(ii) Determine the current that is passing through the battery.

current = [2]

(c) The circuit is then brought outside on a hot sunny day.

(i) How do the resistances ofX andY change?

[2]

(ii) Is the lamp L lighted? Give a reason for your answer.

[2]


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12 EITHER

A stunt man has one end of a thick elastic cord attached to him and the other end ofthe cord is firmly attached to a point on a high bridge. When the man jumps fromthe bridge, he falls freely under gravity for 2.5 s. Take acceleration of free fall to be10 m/s2 and assume that the man is initially at rest.

(a) (i) Calculate the vertical speed the man acquires at the end of his freefall.

vertical speed = [2]

(ii) Sketch a speed-time graph for the vertical motion of the man duringhis free fall. Indicate clearly the speed and time involved. [2]

(iii) Hence, calculate the vertical distance fallen.

vertical distance = [2]

(b) Suggest one reason why, in a real jump, the distance fallen in 2.5 s and thespeed reached would be less than your calculated answers, even though thecord was slack throughout the 2.5 s.

[1]


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After this time the cord begins to stretch and the man continues to fall downward.Eventually his downward acceleration becomes zero.

(c) (i) Explain why his downward acceleration becomes zero.

[2]

(ii) If the mass of the man is 80 kg, suggest a value for the tension in thecord when his downward acceleration is zero.

[1]


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OR

Figure 12.1 shows a roller coaster at an amusement park.

During one run, a car and passengers of total mass 800 kg are released from restat point A, a height of 20 m above the ground. The car travels a distance of 125 malong the track until it reaches point D, a height of 15 m above the ground. Aconstant frictional force of 250 N acts between the car and the track as the carmoves from A to D. The track at CD is horizontal and CD = 5 m.

(a) Calculate the work done against friction in moving from A to C.

work done = [2]

(b) What is the kinetic energy of the car at C?

kinetic energy = [2]

(c) Find the speed of the car as it passes C.

speed = [2]

Apassenger car

20 m15 m

B

C

Figure 12.1

15 m

B

D


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[T

(d) Brakes are applied when the car reaches C so that it stopped at D.

(i) Determine the average braking force exerted on the car.

average breaking force = [2]

(ii) If the total mass of the car is increased and the braking distanceremains unchanged, would the average braking force be greater than,equal to or smaller than before? Explain your answer.

[2]

*** END OF PAPER ***

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