JJC 2012 9646/JC1 CT1 P2/2012 [Turn Over

JURONG JUNIOR COLLEGE JC1 Common Test 2012

Name Class 12S

PHYSICS Higher 2

Structured Questions

Candidates answer on the Question Paper. No Additional Materials are required.

9646/2

29 Jun 2012

1 hour 45 minutes

READ THESE INSTRUCTIONS FIRST Do not open this booklet until you are told to do so. Write your name and class in the spaces provided at the top of this page. Write in dark blue or black pen. You may use a soft pencil for any diagrams, graphs or rough working. Do not use paper clips, highlighters, glue or correction fluid. Answer all questions. 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.

For Examiner’s Use

1

2

3

4

5

6

Total

(This question paper consists of 15 printed pages)

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Data

speed of light in free space, c = 3.00 108 m s1

permeability of free space, o = 4 107 H m1

permittivity of free space, o = 8.85 1012 F m1 = (1/(36)) 109 F m1

elementary charge, e = 1.60 1019 C

the Planck constant, h = 6.63 1034 J s

unified atomic mass constant, u = 1.66 1027 kg

rest mass of electron, me = 9.11 1031 kg

rest mass of proton, mp = 1.67 1027 kg

molar gas constant, R = 8.31 J K1 mol1

the Avogadro constant, NA = 6.02 1023 mol1

the Boltzmann constant, k = 1.38 1023 J K1

gravitational constant, G = 6.67 1011 N m2 kg2

acceleration of free fall, g = 9.81 m s2

Formulae

uniformly accelerated motion, s = ut + 12

at2

v2 = u2 + 2as

work done on/by a gas, W = p V

hydrostatic pressure, p = gh

gravitational potential, =

Gm

r

displacement of particle in s.h.m., x = xo sin t

velocity of particle in s.h.m., v = vo cos t

v = 2 2( )ox x

mean kinetic energy of a molecule of an ideal gas

E = 32

kT

resistors in series, R = R1 + R2 + . . .

resistors in parallel, 1/R = 1/R1 + 1/R2 + . . .

electric potential, V = o

Q

ε r4

alternating current / voltage, x = xo sin t

transmission coefficient, T exp(2kd)

where k = 2

2

8 ( )m U E

h

radioactive decay x = xo exp(-λt)

decay constant λ =

1/2

0.693

t

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1 (a) Distinguish between systematic and random errors.

[2]

(b) State the relationship between base and derived units.

[1]

(c) Provide an SI unit and an estimate of the magnitude of each of the following

physical quantities. (Marks will be awarded for the correct order of magnitude of each estimate, and not for its accuracy.) [2]

SI unit magnitude

Mass of a single deck SBS bus

Thickness of this writing paper

(d) The Young modulus E of a material is given by

Ae

FLE

where F = force exerted on the material,

L = original length of the material, A = cross-sectional area of the material over which the force acts, e = extension of the material.

A teacher performs an experiment to find the Young modulus of an unknown material which is cylindrical in shape. The teacher records the readings as follows:

Force exerted, 10020 ..F N

Original length, 23.0 0.1 10L m

Diameter of the material, 010400 ..d mm

Extension, 010500 ..e mm

(i)

Which measurement will contribute most to the uncertainty in E? [1]

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(ii) Explain how you arrived at your answer.

[2]

(iii) Student A expressed the value of E and its uncertainty as

E = (9.549 ± 0.099) x 109 Pa and student B wrote E = (9.6 ± 0.1) x 109 Pa. Which student expressed E correctly? Give a reason for your answer.

[2]

2 (a) A truck is parked on a steep slope overlooking the ocean, where the slope is at an angle of 37° with the horizontal as shown in Fig. 2. The parking brakes suddenly fail and the truck rolls down the slope with a constant acceleration of 4.0 m s-2 and travels 50 m to the edge of the cliff. The cliff is 30 m above the ocean.

Find

(i) the speed of the truck when it reaches the edge of the cliff,

Speed = m s-1 [1]

370

slope

cliff

sea Fig. 2

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(ii) the speed of the truck when it lands in the ocean,

Speed = m s-1 [3]

(iii) the time the truck is in free fall,

Time = s [1]

(iv) the horizontal distance of the car relative to the base of the cliff when the car first lands in the ocean.

Horizontal distance = m [1]

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(b) When a 10 kg object is falling vertically in air, the air resistance F is given by the equation, F = kv2 where v is the velocity of the object and k has the value

0.042 N s2 m-2.

(i) Explain why the object eventually falls with a uniform velocity (the terminal velocity).

[2]

(ii) Calculate the terminal velocity of the object.

Velocity = m s-1 [2]

3 (a) State the conditions for the equilibrium of a body which is acted upon by a number

of forces.

[2]

(b) Define the moment of a force.

[2]

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(c) A 1.00 m uniform rod of mass 150 kg is supported by a cable perpendicular to the rod as shown in Fig. 3. The rod is hinged at the bottom and a 200 kg object hangs from its top.

(i) Show that the tension in the supporting cable is about 1800 N. [3]

1.00 m

0.75 m

Fig. 3

60o

supporting cable

hinge

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(ii) Determine the magnitude of the horizontal and vertical components of the reaction force exerted on the rod by the hinge.

Vertical component = N

Horizontal component = N [3]

(iii) Hence, determine the magnitude and direction of the force exerted on the rod

by the hinge.

Magnitude = N

Direction = [2]

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(iv) Although the calculated tension in the cable is 1800 N, the cable is usually manufactured to withstand a higher tension for safety reasons. This is termed as “Manufactured Tension” and it is usually designed 2 to 3 times higher than the “Calculated Tension”.

2Manufactured Tension

Factor of SafetyCalculated Tension

Calculate the Manufactured Tension for the cable and provide a reason behind the need for a factor of safety.

Manufactured tension = N [2]

4 (a) State Newton’s Second Law of motion.

[2]

(b) Safety is of major concern when constructing a vehicle. Some makes of car have,

as safety features,

1. regions at the front and rear which are designed to collapse on impact, and

2. the shell of the passenger compartment is of rigid construction.

Using Newton’s Second Law of Motion, explain how the first safety feature could be used to protect passengers from serious injuries in the event of a collision.

[2]

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(c) On an expressway, a Toyota car of mass 1000 kg is travelling at a speed of

90 km h1.

If the car is brought to rest within two seconds, what is the average force experienced by the car?

Average force = N [3]

(d) Suggest two other physical features of a car that could help prevent serious injuries

to the driver and passengers in the vehicle.

[2]

(e) A Mazda car of mass 1250 kg travelling at the speed of 25 m s-1 collides head-on

and locks together with the above Toyota car (travelling at 90 km h-1 in the opposite direction). The collision lasts for 0.20 s.

(i) State the principle of conservation of momentum

[2]

(ii) What is the total momentum of the two cars before the collision?

Total momentum = Ns [1]

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(iii) Calculate the impulse of the Mazda car during the collision.

Impulse =

[3]

5 (a) Energy plays a key part in all branches of Physics and our daily lives. Fig. 5 below

shows the main stages involved in the production of electricity.

Fig. 5

State the energy involved in each stage of the power generation process. [2]

Stage 1

Stage 2

Stage 3

Stage 4

(b)

Derive the equation for kinetic energy 21

2E mv starting from the definition of

work. [3]

Air conditioner

Turbine

Generator

Stage 1 Furnace Stage 2

Stage 3 Stage 4

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(c) The paragraph below is an extract containing some details of an electric car. The Nissan Leaf (also known as "LEAF" as a backronym for Leading,

Environmentally friendly, Affordable, Family car]) is a five-door hatchback electric car manufactured by Nissan and introduced in Japan and the United States in December 2010. The US Environmental Protection Agency quotes an official range of 117 kilometres, with an energy consumption of 765 kilojoules per kilometre and rated the Leaf's combined fuel economy at 2.4 litres/100 km. ( para 2 ) The Nissan Leaf uses a 80 kW and 280 N·m front-mounted synchronous electric motor driving the wheels, powered by a 24 kilowatt-hours lithium ion battery pack rated to deliver up to 90 kW. The Nissan Leaf has a mass of 1521 kg. ( para 3 ) As an all-electric car, the Nissan Leaf produces no tailpipe pollution or greenhouse gas emissions at the point of operation, and reduces dependence on petroleum .

Table 1

Summary of the Nissan Leaf real world operation

Driving condition

AverageSpeed/ km h

-1

Temperature/ 0C

Total drive duration/ min

Range/ km

Air conditioner

City traffic 39 25 263 139 Off

Highway 89 35 76 110 In use

(i) In paragraph 3, it is stated that the Leaf is fitted with a 24 kilowatt-hour

battery. Express 24 kilowatt-hours in joule. [1]

(ii) Using the information in paragraph 2, calculate the energy consumed by the Nissan Leaf in travelling 117 km. [1]

(iii) Given that the Nissan Leaf is powered by an 80 kW electric motor, calculate the minimum time needed to accelerate to 20 m s-1 from a standstill. [2]

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(iv) State your assumption in your answer to part (iii). [1]

(v) The data in table 1 shows that the Nissan Leaf has a longer range and operation time in city traffic compared with driving on the highway. Suggest why this is so.

[2]

(vi) It is commonly thought that switching to electric cars will bring pollution

levels to zero. By considering the current methods used to produce electricity in modern society, discuss whether this commonly held idea is valid?

[2]

6 (a) State the first law of thermodynamics.

[2]

(b) Some water in a saucepan is boiling.

(i) Explain why there is a change in internal energy as water changes to steam.

[2]

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(ii) Explain why temperature of the water remains constant during boiling even though there is a constant supply of thermal energy.

[2]

(c) A fixed mass of ideal gas undergoes a cycle of changes A → B → C → D → A as shown in Fig. 6.

(i) Use Fig. 6 to determine the net work done by the ideal gas in a complete cycle.

Net work done by the ideal gas = J [2]

Volume/ m3

Pressure/

103 Pa

Fig. 6

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(ii) Explain why the total change in the internal energy of the ideal gas in a complete cycle must be zero.

[2]

(iii) If the thermodynamic temperature of the ideal gas at A is 600 K, what is the thermodynamic temperature of the gas at B?

Temperature of the gas at B = K [2]

(iv) Can the thermodynamic cycle illustrated in Fig. 6 be found in a refrigerator or a petrol engine? Explain your answer.

[2]

End of Paper