liu po shan memorial college (2009-10)physics/pastexampapers/2009-2010/... · (2009-10) final...

S.4

Final Exam

PHY

PHYS / S4 / 2009-10 / Final Exam /

Name

Class

Class number

Teacher's Use Only

Section B Question No. Marks

1

2

3

4

5

6

7

8

9

10

Section B Total

Section A Total ____ × 2 = ______

Total marks

LIU PO SHAN MEMORIAL COLLEGE

(2009-10)

FINAL EXAMINATION

PHYSICS Secondary FOUR

Date: 18-6-2010 (Fri)

Time: 2 hours

Question-Answer Book This paper must be answered in English.

1 Write your Name, Class and Class number in the spaces

provided on the this cover. 2 This paper consists of TWO sections, Section A and

Section B. Section A carries 50 marks and Section B carries 80 marks.

3 Answer ALL questions in each section. Write your

answers of both Sections in the spaces provided in this Question-Answer Book.

4 Unless otherwise specified, numerical answers should

be either exact or correct to 3 significant figures. 5 Take g = 10 m s-2.

PHY / S4 / 2009-10 / Final Exam /

Do not write in this margin

Useful Formulae in Physics

(a) Relationships between initial velocity u, uniform acceleration a, final velocity v and displacement travelled s after time t: v = u + at

2

21 atuts +=

asuv 222 += (b) Potential energy gained by a body of mass m when raised through a height h is mgh.

(c) Kinetic energy of a body of mass m moving with speed v is 2

21 mv .

(d) Power = force × velocity

Section A M.C. Questions (50 marks)

1. There are 25 multiple choice questions in this section. Each question carries 2 marks.

2. ANSWER ALL QUESTIONS.

3. You should write down all your answers in the box at the end of each question on this Question-Answer Book.

4. You should write down only ONE answer for each question. If you give more than one answer, you will receive NO MARKS for that question.

5. No marks will be deducted for wrong answers. 1. Which of the following statements about 0 °C are correct? (1) It is the lower fixed point of the Celsius temperature scale. (2) It represents the hotness of pure melting ice at normal atmospheric pressure. (3) It is the temperature at which the average kinetic energy of the particles in an

object is zero. A. (1) and (2) only B. (1) and (3) only C. (2) and (3) only D. (1), (2) and (3)

PHY / S4 / 2009-10 / Final Exam /


2. An ice block of 50 g is taken out from a freezer of –15 °C. Its temperature then

rises from –15 °C to –7 °C. Which of the following expressions shows the energy (in J) absorbed by the ice block?

(Given: specific heat capacity of ice = 2060 J kg–1 °C–1) A. 50 × 2060 × (–7 – 15) B. 50 × 2060 × (–7 + 15)

temperature

time

Z

Y

X

C. 0.05 × 2060 × (–7 – 15) D. 0.05 × 2060 × (–7 + 15) 3. Liquids X, Y and Z of equal mass are heated separately by three identical heaters.

The graph above shows the variation of the temperatures of the liquids with time. Let cX, cY and cZ be the specific heat capacities of X, Y and Z respectively. Which of the following relations is correct?

A. cX = cY > cZ B. cX > cY > cZ C. cX < cY = cZ D. cX > cY = cZ 4. Which of the following cannot increase the rate of evaporation of water? A. Increase the surface area of water. B. Speed up the movement of air. C. Decrease the humidity of air. D. Decrease the temperature of water.

PHY / S4 / 2009-10 / Final Exam /


5. The diagram above shows the apparatus used for finding the specific latent heat

of vaporization of a liquid. The output power of the heater is 200 W. The electronic balance reading decreases by 15 g after the liquid has boiled for 300 s. If the heat lost to the surroundings is ignored, what is the specific latent heat of vaporization of the liquid?

A. 4 × 103 J kg–1 B. 1.2 × 106 J kg–1 C. 4 × 106 J kg–1 D. 6 × 106 J kg–1 6. Which of the following statements about the conduction of heat is/are correct? (1) Metals are generally better conductors than woods. (2) Lighter objects are generally better conductors than heavier objects. (3) Air is a poor conductor.

A. (1) only B. (2) only C. (1) and (3) only D. (2) and (3) only

PHY / S4 / 2009-10 / Final Exam /

7.


Two solid substances A and B of equal mass are heated by two identical heaters at

the same power. The temperature−time graph is shown above. Which of the following statements is not correct?

A. The melting point of solid A is 120 °C. B. The melting point of solid B is higher than that of solid A. C. The specific latent heat of fusion of solid B is greater than that of solid A. D. The specific heat capacity of solid B is larger than that of solid A. 8. The apparatus shown above is used to find the specific latent heat of fusion of ice.

Which of the following is/are the precaution(s) for giving an accurate result? (1) Use ice of temperature well below 0 °C. (2) Insert the heating part of each immersion heater into the ice completely. (3) Cover the funnels with lids. A. (1) only B. (2) only C. (1) and (3) only D. (2) and (3) only

PHY / S4 / 2009-10 / Final Exam /


9. In some airports, infrared detectors are used to measure the body temperature of

the visitors. Which of the following heat transfer processes is/are it based on?

(1) Radiation (2) Convection (3) Conduction


10.

X Y

A

B

C

Three girls A, B and C run from point X to point Y along different paths as shown above. They take the same amount of time to complete the journey. Which of the following statements are correct?

(1) The girls travel with constant velocity. (2) The girls have the same average velocity. (3) Girl A has the highest speed.

A. (1) and (2) only B. (1) and (3) only C. (2) and (3) only D. (1), (2) and (3)

11. Which of the following statements is/are correct?

(1) An object moving at a constant speed must have zero acceleration. (2) An object with zero velocity can be accelerating. (3) An object having zero acceleration can have varying velocity.


PHY / S4 / 2009-10 / Final Exam /

12.


The velocity−time graph of the motion of a car is shown above. Which of the

following shows the acceleration−time graph of the car?

A. B. C. D. 13. Ball A weighs W on Earth and ball B weighs the same on the Moon. Now ball A

on Earth and ball B on the Moon are projected vertically upwards at the same speed. Which of the following statements is/are correct? The acceleration due to gravity on Earth is 6 times that on the Moon. (1) The mass of ball A is greater than ball B. (2) Neglecting air resistance, their speeds just before they return to the ground

are the same. (3) They reach the same maximum height, neglecting air resistance. A. (1) only B. (2) only C. (1) and (3) only D. (2) and (3) only

PHY / S4 / 2009-10 / Final Exam /

14.


v / m s−1

t / s

10

2 0

4 6 8 10 12

5

−5

−10

The velocity-time (v-t) graph of a car travelling on a straight road is shown above. What is the average velocity of the car from t = 0 to t = 12 s?

A. 5.83 m s−1 B. 6.67 m s−1 C. 7.50 m s−1 D. 8.33 m s−1

15. Mass A of 10 kg and mass B of 15 kg are connected by a light inelastic string

passing over a smooth pulley. Initially mass A is on the ground while mass B is hung 10 m above the ground. Mass B is then released. What is the greatest height above the ground reached by mass A?

A. 10 m B. 12 m C. 13 m D. 15 m

PHY / S4 / 2009-10 / Final Exam /

16.


W

θ

T1 ball

A ball is connected to the ceiling and the wall by two light and inextensible strings as shown above. The tension T1 in the left string is perpendicular to the weight W of the ball. The right string makes an angle of θ with the vertical. What is the relationship between T1, W and θ?

A. WT1cos =θ

B. WT1sin =θ

C. WT1tan =θ

D. 1

tanTW

=θ

17. Michael jumps up vertically and reaches a height of 1 m as shown above. The

mass of Michael is 90 kg and the air resistance acting on him is 10 N on average.What are his speeds when he leaves the ground and reaches the ground?

Speed when leaving

the ground / m s−1 Speed when reaching

the ground / m s−1

A. 4.45 4.50 B. 4.47 4.47 C. 4.50 4.45 D. 4.50 4.50

PHY / S4 / 2009-10 / Final Exam /


18. Which of the following processes involve a rate of energy transfer of 50 W? (1) A 5-kg mass decelerates from 10 m s−1 to rest in 5 seconds. (2) A 2-kg mass is raised vertically upwards for 5 m in 4 seconds. (3) A 3-kg mass on a rough horizontal table is pushed by a 25-N horizontal force

and moves at a constant speed of 2 m s−1. A. (1) and (2) only B. (1) and (3) only C. (2) and (3) only D. (1), (2) and (3) 19. A block of mass 0.5 kg initially travelling at a uniform speed of 2 m s−1 collides

head-on with another object. The graph above shows how the force F acting on the block by the object varies with time t. Which of the following statements is/are correct? (1) The collision time is about 0.5 s. (2) The average force acting on the block during the collision is 2.5 N. (3) The block is brought to rest after the collision. A. (1) and (2) only B. (1) and (3) only C. (2) and (3) only D. (1), (2) and (3)

PHY / S4 / 2009-10 / Final Exam /


20. A worker is pulling a trolley with goods placed above on a smooth horizontal

path as shown above. The masses of the trolley and the goods are 5 kg and 75 kg respectively. Given the maximum frictional force between the trolley and the goods is 120 N. What is the maximum acceleration of the trolley such that the goods do not slip?

A. 1.50 m s-2 B. 1.60 m s-2

400 m s- 1

C. 1.71 m s-2 D. 24.0 m s-2

21.

A bullet of 5 g is fired horizontally from a gun of mass 0.75 kg. Suppose the bullet leaves the barrel at a speed of 400 m s−1 as shown above. Which of the following statements is/are correct?

(1) Both the momentum and total kinetic energy of the bullet and the gun are conserved before and after the bullet is fired. (2) The recoil speed of the gun is 2.67 m s−1.

(3) If the mass of the gun is doubled, the recoil speed is halved. A. (1) only B. (2) only C. (1) and (2) only D. (2) and (3) only

PHY / S4 / 2009-10 / Final Exam /


22. A ray of light travels from liquid X to the air as shown above. What is the

refractive index of liquid X? A. 1.31 B. 1.50 C. 1.85 D. 2.00

23. A ray of light enters a glass prism as shown below, which path best represents

how the light ray leaves the prism? Take the refractive index of the glass to be 1.52.

PHY / S4 / 2009-10 / Final Exam /


24. An object O is placed in front of a lens L. The figure above shows the positions

of the object, the lens and the image I formed by the lens. What is the type of lens L and its focal length f ?

L f A. convex lens 8.5 cm B. convex lens 17 cm C. concave lens 8.5 cm D. concave lens 17 cm

PHY / S4 / 2009-10 / Final Exam /


25.

10 cm

O

F F

An object O is initially placed 30 cm in front of a convex lens of focal length 20 cm as shown above. Then the object is moved 5 cm away from the lens.

Which of the following statements best describe(s) the image? (1) The size of the image becomes smaller. (2) The image changes from inverted to erect. (3) The image changes from real to virtual.


- END OF SECTION A -

PHY / S4 / 2009-10 / Final Exam /


SECTION B Conventional Questions (80 marks) Answer ALL questions in this section and write your answers in the spaces provided in this Question-Answer Book.

Question No. 1 2 3 4 5 6 7 8 9 10

Marks 8 6 7 7 4 13 9 12 9 5

1. Figure 1.1 Figure 1.2 Peter cooks an instant noodle with a microwave oven of power 1 kW. He first

adds the noodle into 500 g of 60 °C hot water as shown in Figure 1.1. Then, he heats the bowl of noodle and water with a microwave oven (Figure 1.2). Assume that all the energy supplied by the microwave oven is absorbed by the water.

(Given: specific heat capacity of water = 4200 J kg−1 °C−1, specific latent heat of vaporization of water = 2.26 × 106 J kg−1.) (a) (i) Calculate the energy required to boil the water. (2 marks) _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________

PHY / S4 / 2009-10 / Final Exam /


(ii) How long does it take for the microwave oven to boil the water? (2 marks) _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ (b) After the water starts boiling, cooking lasts for another 2 minutes. How much

water is vaporized? (3 marks) ______________________________________________________________ ______________________________________________________________ ______________________________________________________________ ______________________________________________________________ ______________________________________________________________ ______________________________________________________________ (c) State one advantage of covering the bowl during cooking. (1 mark) ______________________________________________________________ ______________________________________________________________ ______________________________________________________________

PHY / S4 / 2009-10 / Final Exam /

2.

Do not write in this margin B

A Figure 2

Two identical sealed metal cans A and B are filled with the same amount of water. Half the outer wall of each can is painted black and the other half is painted white. The two cans are placed under the sunlight as shown in Figure 2. Assume that the same amount of sunlight falls on the black half and the white half of the two cans.

(a) Explain why the temperature of water in the cans increase after a few hours. (2 marks) ______________________________________________________________ ______________________________________________________________ ______________________________________________________________ ______________________________________________________________ ______________________________________________________________ ______________________________________________________________ (b) In which can will the water has a higher average temperature after a few

hours? Explain briefly. (4 marks) ______________________________________________________________ ______________________________________________________________ ______________________________________________________________ ______________________________________________________________ ______________________________________________________________ ______________________________________________________________ ______________________________________________________________ ______________________________________________________________ ______________________________________________________________ ______________________________________________________________

PHY / S4 / 2009-10 / Final Exam /

3.


Figure 3 Besides being delicious, ice-cream makes us feel cool in the hot summer (as

shown in Figure 3). This question is to estimate how much it can cool us down. Given the specific latent heat of fusion of ice-cream is 3.34 × 105 J kg–1.

(a) Consider a boy of mass 30 kg eats 0.3 kg of ice-cream at 0 °C, calculate the

energy lost by the boy after eating the ice-cream (2 marks) ______________________________________________________________ ______________________________________________________________ ______________________________________________________________ ______________________________________________________________ (b) The specific heat capacity of the human body is close to that of water which

equals to 4200 J kg–1 °C–1. Explain briefly. (1 mark) ______________________________________________________________ ______________________________________________________________ ______________________________________________________________ (c) Find the drop in his body temperature after eating the ice-cream. (2 marks) ______________________________________________________________ ______________________________________________________________ ______________________________________________________________ ______________________________________________________________ (d) State one assumption in the above estimation of drop in body temperature. (2 marks) ______________________________________________________________ ______________________________________________________________ ______________________________________________________________

PHY / S4 / 2009-10 / Final Exam /

4.


Figure 4

5 cm

1 m s−1putter

Figure 4 shows a 0.046 kg golf ball at rest is struck by a putter. The golf ball moves a distance of 5 cm during which it remains in contact with the putter. Then it moves with a uniform velocity of 1 m s-1.

(a) Find the average acceleration of the golf ball when it is in contact with the

putter. (3 marks) _____________________________________________________________ _____________________________________________________________ _____________________________________________________________ _____________________________________________________________ _____________________________________________________________ (b) Find the force exerted by the putter on the golf ball. Given the friction

acting on the golf ball is 2N. (2 marks) _____________________________________________________________ _____________________________________________________________ _____________________________________________________________ _____________________________________________________________ (c) Find the work done by the putter when it is in contact with the golf ball. (2 marks) _____________________________________________________________ _____________________________________________________________ _____________________________________________________________

PHY / S4 / 2009-10 / Final Exam /

5.


block

string

lift

Figure 5.1

Figure 5.1 shows a 2 kg block is tied to one end of a string. The other end of the string is fixed to the ceiling of a lift, which is moving upwards. The variation of the tension of the string with time is shown in Figure 5.2 below.

tension / N

time / s 0

20

t1 t2 t3

Figure 5.2 (a) Describe the motion of the lift during the time interval

(i) t ______________________________________________ (1 mark) 1

2

(ii) t ______________________________________________ (1 mark)

(b) A student suggests that the tension in the string and the weight of the block form an action-reaction pair. Explain whether the suggestion is correct or not. (2 marks)

_____________________________________________________________ _____________________________________________________________ _____________________________________________________________

PHY / S4 / 2009-10 / Final Exam /

12 m s−1

6.


Figure 6

Figure 6 shows a spacecraft of mass 20 000 kg is going to land on the moon. The spacecraft descends with a constant velocity of 12 m s-1. It is known that the acceleration due to gravity on the moon is 1.6 m s-2.

(a) Find the upward thrust developed by the spacecraft’s engine. (2 marks) _____________________________________________________________ _____________________________________________________________ _____________________________________________________________ _____________________________________________________________ (b) The upward thrust is then increased to 42 000 N. The spacecraft decelerates

uniformly and lands on the moon’s surface after 20 s. (i) Show that the deceleration of the spacecraft is 0.5 m s-2. (3 marks) _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________

PHY / S4 / 2009-10 / Final Exam /


(ii) Find the landing speed of the spacecraft. (2 marks) _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ (iii) Find the distance travelled by the spacecraft during the deceleration.

(2 marks) _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________

(c) A student suggests that we can use a small stone and a stop watch to

estimate the acceleration due to gravity on the moon. Describe briefly how this can be done. (4 marks)

_____________________________________________________________ _____________________________________________________________ _____________________________________________________________ _____________________________________________________________ _____________________________________________________________ _____________________________________________________________ _____________________________________________________________ _____________________________________________________________ _____________________________________________________________

PHY / S4 / 2009-10 / Final Exam /

7. Do not write

in this margin

Figure 7 Figure 7 shows a man of mass 60 kg is going to take a bungee jump from a

bridge of height 100 m above a river. His legs are tied with a light and elastic string of length 50 m. Neglect the air resistance and take the gravitational potential energy at the surface of the river as zero.

(a) Find the gravitational potential energy of the man when he is on the bridge. (2 marks) _____________________________________________________________ _____________________________________________________________ _____________________________________________________________ _____________________________________________________________ _____________________________________________________________

(b) Find the speed of the man when he is 70 m above the river. (2 marks) ____________________________________________________________

_____________________________________________________________ _____________________________________________________________ _____________________________________________________________ _____________________________________________________________ _____________________________________________________________

PHY / S4 / 2009-10 / Final Exam /


(c) The string stretches for 20 m before the man comes to rest at the lowest position.

(i) Find the elastic potential energy of the string when the man is at the

lowest position. (2 marks)

_________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________

(ii) Find the average force acting on the man by the string when the man falls from 50 m below the bridge to 70 m below the bridge.

(3 marks) _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________

PHY / S4 / 2009-10 / Final Exam /

8.


trolley

θ

A

B C

Figure 8.1

Figure 8.1 shows a 1 kg trolley is released from rest at the top of a runway ABC. The runway consists of a smooth inclined plane AB and a rough horizontal plane BC. The speed-time graph of the trolley is shown below (Figure 8.2).

Figure 8.2

speed / m s−1

time / s0 2

6

10

(a) (i) Find the acceleration of the trolley as it travels down AB. (2 marks)

_________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ (ii) Find the angle of inclination θ. (2 marks) _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________

PHY / S4 / 2009-10 / Final Exam /

Do not write margin

in this

(iii) Find the length of AB. (2 marks)

_________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________

(b) Find the friction acting on the trolley when it is travelling on BC.

(3 marks) _____________________________________________________________ _____________________________________________________________ _____________________________________________________________ _____________________________________________________________ _____________________________________________________________ _____________________________________________________________ (c) Suppose the trolley is projected up the runway from C. Sketch a graph to

show the variation of the speed of the trolley as it travels from C to A. (3 marks)

speed

time 0

PHY / S4 / 2009-10 / Final Exam /

9.


5 cm

object

Figure 9

An object is placed 15 cm in front of a lens as shown in Figure 9.

(a) What kind of lens is used? (1 mark)

_____________________________________________________________

(b) (i) In Figure 9, complete the ray diagram to locate the image of AB. (3 marks)

(ii) Find the magnification of the image. (2 marks) _________________________________________________________ _________________________________________________________

(iii) Find the focal length of the lens. (1 mark)

Focal length = __________ cm.

(c) Use the lens formula to find the image distance if the object is now place 10 cm in front of the lens. (2 marks)

_____________________________________________________________ _____________________________________________________________ _____________________________________________________________ _____________________________________________________________

PHY / S4 / 2009-10 / Final Exam /

r / degree

i / degree0 24.4

90

10.


Figure 10

A ray of light travels from medium P to air. The variation of the angle of incidence i with the angle of refraction r is shown in Figure 10. (a) Explain what happens to the light ray when i is greater than 24.4°.

(1 mark) ____________________________________________________________

(b) (i) Find the refractive index of P. (2 marks)

________________________________________________________ ________________________________________________________ ________________________________________________________ (ii) Find the value of r when i is 15°? (2 marks) ________________________________________________________ ________________________________________________________ ________________________________________________________ ________________________________________________________

- END OF SECTION B -

End of Paper

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