Erzurum İhsan Doğramacı Foundation Bilkent Laboratory School

2012-13 School Year11th SL Grade

Physics Exam #2Name

Student ID#

Date December 2012

Time Allowed 75 mins

INSTRUCTIONS: It is strictly forbidden to share any material such as pencil, eraser, ruler

etc. You are not allowed to ask the teacher any type of question related with

the meaning of the questions Read the questions very carefully and make sure your answers are clearly

explained and showed Calculators may be used. Do not open this examination paper until instructed to do so.-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- Section A: Answer all of questions 1-15 b writing your answers on

the cover page.

Section B: Answer all of 16-20 question in the spaces provided.-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- This booklet consists of 13 numbered pages

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Section A: Answer all of questions 1-15 b writing your answers on the cover page.

Question 1. The kinetic energy of a mass m is given by ½ mv2. If the speed v is trippled, by what factor does the energy change?

A. Increase by a factor of 3B. Increase by a factor of √ 3C. Increase by a factor of 6D. Increase by a factor of 9

(1)

Question 2. The electric force between two charges Q1 and Q2, a distance r apart, is given by the equation f =k Q1. Q 2

r2 , where k is a constant. If both charges double, but the force between them remains the same, by what factor did their separationchange?

A. Increased by a factor of 2B. Increased by a factor of 4C. Decreased by a factor of 2D. Decreased by a factor of 4

(1)

Question 3.

The graph shows the variation with time t of the velocity v of an object.

Total

Question#

1 2 3 4 5 6 7 8 9 10

11

12

13

14

15

16

17

18

19

20

60 pts

Answer

11p 6 5 6 17

PointsEarned

-3-v

t

Which one of the following graphs best represents the variation with time t of the acceleration a of the object?

0 0

0 0

0 0

0 0

a a

a a

t t

t t

A . B .

C . D .

(1)

Question 4.

A rocket is fired vertically. At its highest point, it explodes. Which one of the following describes what happens to its total momentum and total kinetic energy as a result of the explosion?

Total momentum Total kinetic energy

A. unchanged increased

B. unchanged unchanged

C. increased increased

D. increased unchanged

(1)

Question 5.

Two satellites of equal mass, S1 and S2, orbit the Earth. S1 is orbiting at a distance r from the

Earth’s centre at speed v. S2 orbits at a distance 2r from the Earth’s centre at speed 2v

. The ratio of the centripetal force on S1 to the centripetal force on S2 is

-4-

A. 81

.

B. 41

.

C. 4.

D. 8.(1)

Question 6.

The specific latent heat of vaporization of a substance is the quantity of energy required to

A. raise the temperature of a unit mass of a substance by one degree Celsius.

B. convert a unit mass of liquid to vapour at constant temperature and pressure.

C. convert a unit mass of solid to vapour at constant temperature and pressure.

D. convert a unit mass of liquid to vapour at a temperature of 100°C and a pressure of one atmosphere.

(1)

Question 7.

The graph below shows the current/voltage characteristics of a filament lamp.

2 4

1 6

8

0 0 2 4 6 8 1 0Vo lta g e / V

C u rre n t / × 1 0 A– 3

The resistance of the filament at 4.0 V is

A. 250 Ω.

B. 4 000 Ω.

C. 8 000 Ω.

D. 64 000 Ω.(1)

Question 8.

The diagram below shows the variation with displacement x of the force F acting on an object in the direction of the displacement.

-5-F

xxx

P

Q

R

S

TVW210

0

Which area represents the work done by the force when the displacement changes from x1 to x2?

A. QRS

B. WPRT

C. WPQV

D. VQRT(1)

Question 9.

A ball is released from rest near the surface of the Moon. Which one of the following quantities increases at a constant rate?

A. Only distance fallen

B. Only speed

C. Only speed and distance fallen

D. Only speed and acceleration(1)

Question 10.

Two different objects are in thermal contact with one another. The objects are at different temperatures. The temperatures of the two objects determine

A. the process by which thermal energy is transferred.

B. the heat capacity of each object.

C. the direction of transfer of thermal energy between the objects.

D. the amount of internal energy in each object.(1)

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Question 11.

The time period T of oscillation of a mass m suspended from a vertical spring is given by the expression

T = 2π km

where k is a constant.

Which one of the following plots will give rise to a straight-line graph?

A. T2 against m

B. T against m

C. T against m

D. T against m(1)

Question 12.

Peter and Susan both stand on the edge of a vertical cliff.

S e a

V (P e te r)

V (S u sa n )

Susan throws a stone vertically downwards and, at the same time, Peter throws a stone vertically upwards. The speed V with which both stones are thrown is the same. Neglecting air resistance, which one of the following statements is true?

-7-A. The stone thrown by Susan will hit the sea with a greater speed than the stone

thrown by Peter.

B. Both stones will hit the sea with the same speed no matter what the height of the cliff.

C. In order to determine which stone hits the sea first, the height of the cliff must be known.

D. In order to determine which stone hits the sea first both the height of the cliff and the mass of each stone must be known.

(1)

Question 13.

A small electrically charged sphere is suspended vertically from a thread. An oppositely charged rod is brought close to the sphere such that the sphere is in equilibrium when displaced from the vertical by an angle of 45°.

+ –

Which one of the following best represents the free body diagram for the sphere?

A .

C .

B .

D .

(1)

-8-Question 14.

An elevator (lift) is used to either raise or lower sacks of potatoes. In the diagram, a sack of potatoes of mass 10 kg is resting on a scale that is resting on the floor of an accelerating elevator. The scale reads 12 kg.

1 0 k ge le v a to r

sca le

The best estimate for the acceleration of the elevator is

A. 2.0 m s–2 downwards.

B. 2.0 m s–2 upwards.

C. 1.2 m s–2 downwards.

D. 1.2 m s–2 upwards.(1)

Question 15.

The specific latent heat of fusion of a substance is defined as the amount of thermal energy required to change the phase of

A. the substance at constant temperature.

B. unit mass of the substance to liquid at constant temperature.

C. unit mass of the substance at constant temperature.

D. the substance to gas at constant temperature.(1)

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Section B: Answer all of 16-20 question in the spaces provided.

Question 16. This question is about an experiment designed to investigate Newton’s second law.

In order to investigate Newton’s second law, David arranged for a heavy trolley to be accelerated by small weights, as shown below. The acceleration of the trolley was recorded electronically. David recorded the acceleration for different weights up to a maximum of 3.0 N. He plotted a graph of his results.

h ea v y tro lle y a cce le ra tio np u lle y

w e ig h t

(a) Describe the graph that would be expected if two quantities are proportional to one another.

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-10- (b) David’s data are shown below, with uncertainty limits included for the value of the weights.

Draw the best-fit line for these data.

1 .4 0

1 .2 0

1 .0 0

0 .8 0

0 .6 0

0 .4 0

0 .2 0

0 .0 00 .0 0 0 .5 0 1 .0 0 1 .5 0 2 .0 0 2 .5 0

w e ig h t / N

a c ce le ra tio n/ m s – 2

(2)

(c) Use the graph to

(i) explain what is meant by a systematic error.

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(ii) estimate the value of the frictional force that is acting on the trolley.

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(iii) estimate the mass of the trolley.

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(Total 9 marks)

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Question 17. (a) A small lump of ice (a hailstone) at 0°C falls to the Earth’s surface. When the hailstone hits

the surface, all of the kinetic energy of the hailstone is transferred to thermal energy in the ice. Calculate the minimum speed of the hailstone so that it just melts when it hits the surface. The specific latent heat of fusion of ice is 340 kJ kg–1.

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(b) By reference to your answer in (a), suggest whether hailstones are likely to melt on hitting the Earth’s surface.

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(Total 5 marks)

Question 18.

. Some students were asked to design and carry out an experiment to determine the specific latent heat of vaporization of water. They set up the apparatus shown below.

V

AW a te r

H ea te r

To p -p a n b a lan ce

d .c . su p p ly

g

The current was switched on and maintained constant using the variable resistor. The readings of the voltmeter and the ammeter were noted. When the water was boiling steadily, the reading of

-12-the top-pan balance was taken and, simultaneously, a stopwatch was started. The reading of the top-pan balance was taken again after 200 seconds and then after a further 200 seconds.

The change in reading of the top-pan balance during each 200 second interval was calculated and an average found. The power of the heater was calculated by multiplying together the readings of the voltmeter and the ammeter.

(a) Suggest how the students would know when the water was boiling steadily.

.....................................................................................................................................

.....................................................................................................................................(1)

(b) Explain why a reading of the mass lost in the first 200 seconds and then a reading of the mass lost in the next 200 second interval were taken, rather than one single reading of the mass lost in 400 seconds.

(2)

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The students repeated the experiment for different powers supplied to the heater. A graph of the power of the heater against the mass of water lost (the change in balance reading) in 200 seconds was plotted. The results are shown below. (Error bars showing the uncertainties in the measurements are not shown.)

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1 2 0

1 0 0

8 0

6 0

4 0

2 0

0

p o w e r / W

0 1 2 3 4 5 6 7 8m ass / g

(c) (i) On the graph above, draw the best-fit straight line for the data points.(1)

(ii) Determine the gradient of the line you have drawn.

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...........................................................................................................................(3)

In order to find a value for the specific latent heat of vaporization L, the students used the equation

P = mL,

where P is the power of the heater and m is the mass of water evaporated per second.

(d) Use your answer for the gradient of the graph to determine a value for the specific latent heat of vaporization of water.

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(3)

(e) The theory of the experiment would suggest that the graph line should pass through the origin. Explain briefly why the graph does not pass through the origin.

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.....................................................................................................................................(2)

(Total 12 marks)

Question 19.

. This question is about throwing a stone from a cliff.

Antonia stands at the edge of a vertical cliff and throws a stone vertically upwards.

S e a

v = 8 .0 m s – 1

The stone leaves Antonia’s hand with a speed v = 8.0ms–1.

The acceleration of free fall g is 10 m s–2 and all distance measurements are taken from the point where the stone leaves Antonia’s hand.

-15-(a) Ignoring air resistance calculate

(i) the maximum height reached by the stone.

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...........................................................................................................................(2)

(ii) the time taken by the stone to reach its maximum height.

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...........................................................................................................................(1)

The time between the stone leaving Antonia’s hand and hitting the sea is 3.0 s.

(b) Determine the height of the cliff.

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.....................................................................................................................................(3)

(Total 6 marks)

Question 20.

Simple harmonic motion and the greenhouse effect

(a) A body is displaced from equilibrium. State the two conditions necessary for the body to execute simple harmonic motion.

1. .........................................................................................................................

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2. .........................................................................................................................

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-16- (b) In a simple model of a methane molecule, a hydrogen atom and the carbon atom can be

regarded as two masses attached by a spring. A hydrogen atom is much less massive than the carbon atom such that any displacement of the carbon atom may be ignored.

The graph below shows the variation with time t of the displacement x from its equilibrium position of a hydrogen atom in a molecule of methane.

The mass of hydrogen atom is 1.7 10–27 kg. Use data from the graph above

(i) to determine its amplitude of oscillation.

.........................................................................................................................(1)

(ii) to show that the frequency of its oscillation is 9.1 1013 Hz.

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.........................................................................................................................(2)

(iii) to show that the maximum kinetic energy of the hydrogen atom is 6.2 10–18 J.

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(c) On the grid below, sketch a graph to show the variation with time t of the speed v of the hydrogen atom for one period of oscillation starting at t = 0. (There is no need to add values to the speed axis.)

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(3)

(d) Assuming that the motion of the hydrogen atom is simple harmonic, its frequency of oscillation f is given by the expression

,21

pmkf

where k is the force per unit displacement between a hydrogen atom and the carbon atom and mp is the mass of a proton.

(i) Show that the value of k is approximately 560 N m–1.

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(ii) Estimate, using your answer to (d)(i), the maximum acceleration of the hydrogen atom.

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(e) Methane is classified as a greenhouse gas.

(i) Describe what is meant by a greenhouse gas.

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.........................................................................................................................(2)

(ii) Electromagnetic radiation of frequency 9.1 1013 Hz is in the infrared region of the electromagnetic spectrum. Suggest, based on the information given in (b)(ii), why methane is classified as a greenhouse gas.

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(Total 17 marks)