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Emission Spectrum - Physics - Exam Paper, Exams of Physics

These are the notes of Exam Paper of Physics. Key important points are: Emission Spectrum, Free Electrons,, Maximum Energy Output, Solar Panel, Incandescent Light Bulbs, Fraction of Energy, Function of Voltage, Kinetic Energy

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CAP High School Prize Exam
10 March 2011
9:00 - 12:00
Competitor’s Information Sheet
The following information will be used to inform competitors and schools of the exam results, to determine
eligibility for some subsequent competitions, and for statistical purposes. Only the marking code, to be assigned
by the local examination committee, will be used to identify papers for marking.
Marking Code:
This box must be left empty.
PLEASE PRINT CLEARLY IN BLOCK LETTERS
Family Name: Given Name:
Home Address:
Postal Code:
Telephone: ( ) Email:
School: Grade:
Physics Teacher:
Date of Birth: Sex: Male Female
Citizenship: or
Immigration Status:
For how many years have you studied in a Canadian school?
Would you prefer the further correspondence in French or English?
Sponsored by:
Canadian Association of Physicists,
Canadian Physics Olympiad,
University of British Columbia,
Department of Physics and Astronomy.
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CAP High School Prize Exam

10 March 2011

Competitor’s Information Sheet

The following information will be used to inform competitors and schools of the exam results, to determine

eligibility for some subsequent competitions, and for statistical purposes. Only the marking code, to be assigned

by the local examination committee, will be used to identify papers for marking.

Marking Code:

This box must be left empty.

PLEASE PRINT CLEARLY IN BLOCK LETTERS

Family Name: Given Name:

Home Address:

Postal Code:

Telephone: ( ) Email:

School: Grade:

Physics Teacher:

Date of Birth: Sex: Male Female

Citizenship: or

Immigration Status:

For how many years have you studied in a Canadian school?

Would you prefer the further correspondence in French or English?

Sponsored by:

Canadian Association of Physicists,

Canadian Physics Olympiad,

University of British Columbia,

Department of Physics and Astronomy.

Canadian Association of Physicists

2011 Prize Exam

This is a three-hour exam. National ranking and prizes

will be based on students performance on sections A

and B of the exam. Performance on the questions in

parts A will be used to determine whose written work

in part B will be marked for prize consideration by the

CAP Exam National Committee. Part A consists of

twenty-three multiple-choice questions. The questions

in part B span a range of difficulties, and may require

graphing. Be careful to gather as many of the easier

marks as possible before venturing into more difficult

territory. If an answer to part (a) of a question is

needed for part (b), and you are not able to solve part

(a), assume a likely solution and attempt the rest of

the question anyway.

Non-programmable calculators may be used. Please

be careful to answer the multiple-choice questions on

the answer card/sheet provided; most importantly,

write your solutions to the three long problems on

three separate sheets as they will be marked by peo-

ple in different parts of Canada. Good luck.

Notice: Full marks will be given to a student who

provides any full correct solution to the long problems.

Partial marks will be given for partial solutions. There

are no penalties for incorrect answers. The questions

are not of equal difficulty. Remember we are challeng-

ing the best physics students in Canada; it is possible

that even the best papers may not achieve an overall

score of 80%. This is meant to be tough!

Data

Speed of light c = 3. 00 × 10

m/s

Gravitational constant G = 6. 67 × 10

Nm

/kg

Acceleration due to gravity g = 9.80 m/s

Density of fresh water ρ = 1. 00 × 10

kg/m

The normal atmospheric pressure P

= 1. 01 × 10

Pa

The specific heat of water c = 4. 186 × 10

J/kgK

Fundamental charge e = 1. 60 × 10

C

Mass of electron m

e

= 9. 11 × 10

kg

Mass of proton m

p

= 1. 67 × 10

kg

Planck’s constant h = 6. 63 × 10

Js

Coulomb’s constant 1/(4πǫ

) = 8. 99 × 10

Nm

/C

Boltzmann’s constant k = 1. 38 × 10

J/K

A.U. Astronomical Unit = 1. 49598 × 10

m The ap-

proximate distance from the Sun to the Earth.

Radius of the Earth = 6. 371 × 10

m

Linear expansion coefficient of iron

Fe

= 1. 1 × 10

K

Linear expansion coefficient of zinc

Zn

= 3. 0 × 10

K

1 US mile = 1609 meters

1 US gallon = 3.785 liters

Part A: Multiple Choice

Question 1

Incandescent light bulbs are notorious for being rela-

tively inefficient in producing visible light. The tung-

sten wire inside such a bulb is at a temperature of

approximately 3000 K and the emission spectrum is

very similar to that of a blackbody. The efficiency is

so low because

a) Most of the electrons are absorbed in the tungsten

wire.

b) Most of the power is lost due to the resistance of

the bulb.

c) The electric power actually is efficiently transformed

into radiation but at 3000 K, most of it is infrared.

d) A blackbody absorbs more light than it emits, hence

it appears black.

Question 2

A solar panel installed on a spaceship has a maximum

energy output of 5 kW near the Earth. What is the

maximum energy output of the solar panel when the

spaceship is near Mars? (The distance from the Earth

to the Sun is 1 A.U. and from Mars to the Sun is

1.5 A.U.)

(a) 3.3 kW; (b) 2.2 kW; (c) 1.0 kW;

(d) 0.55 kW; (e) 0.20 kW.

Question 3

A scientist measured a 1μA current in an area of a hu-

man brain. Unlike current in metals which is carried

by free electrons, the current in the brain is mainly car-

ried by potassium ions. Each potassium ion has one

unit of charge e. This current corresponds to the flow

of how many potassium ions per second?

(a) 6 × 10

; (b) 6 × 10

; (c) 6 × 10

(d) 6 × 10

; (e) 6 × 10

Question 4

The gas supply to your physics professor’s house sud-

denly stops due to a gas line failure. It is winter and

the temperature outside is − 5

C and constant. As-

suming all the doors and windows remain closed, which

of these graphs best describes how the temperature in

the house changes with time after the gas supply stops?

(a)

Time (hours)
Temperature

C

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

....

...........

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.

..........

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..

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(b)

Time (hours)
Temperature

C

.

.........

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(c)

Time (hours)
Temperature

C

.

.....

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

(d)

Time (hours)
Temperature

C

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

.....

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Question 14

A huge case, attached to a cable, is descending at a

constant velocity. The tension in the cable is (neglect-

ing the air resistance):

a) greater than the weight of the case.

b) smaller than the weight of the case.

c) equal to the weight of the case.

d) we cannot tell since we dont know the weight of the

case.

Question 15

Objects A and B, isolated from the environment, are

initially separated from each other and are then placed

in thermal contact. Their initial temperatures are

T

A

C and T

B

C. The heat capacity of B

is twice the one of A. After a certain time, the system

reaches equilibrium. The final temperatures are:

C

1.0Kg

A

C

2.0Kg

B

a) T

A

= T

B

C.

b) T

A

= T

B

C.

c) T

A

= T

B

C.

d) T

A

> T

B

C.

e) T

A

C > T

B

Question 16

When a car is starting, its driving wheels experience:

a) The force of kinetic friction directed backward.

b) The force of static friction directed backward.

c) The force of kinetic friction directed forward.

d) The force of static friction directed forward.

Question 17

An aquarium partly filled with water accelerates down

an incline which is at an angle θ with respect to the

horizon. The surface of water in the aquarium:

a) is horizontal.

b) is parallel to the plane of the incline.

c) forms an angle α with the horizon, where 0

d) forms an angle α with horizon, where θ < α < 90

Question 18

Objects around us have different colours. This is be-

cause

a) They are at different temperatures.

b) They are non-thermal radiation sources.

c) Different materials or paints reflect light at different

speeds.

d) Different materials or paints reflect different wave-

lengths.

Question 19

This graph shows the average temperature inside a

room. At time t

the heater is turned on. We want

to compare the power input to the room (P

in

) and

the power output from the room (P

out

). For which

region(s) on the graph is P

in

= P

out

Temp
Time

t

t

I II III

a) Only region I.

b) Only region II.

c) Only region III.

d) Only regions I &

III.

e) Regions I, II & III.

Question 20

A spherical asteroid with a radius of 1 km is illumi-

nated by sunlight. In order to calculate the solar power

absorbed by the asteroid, what area should be used?

a) 1 km

b) 3.14 km

c) 12.6 km

d) Answer cannot be determined from the available

data.

Question 21

If you toss a ball up, at the highest point

a) The velocity changes direction.

b) The acceleration changes direction.

c) The acceleration is zero.

d) Both velocity and acceleration are zero.

e) More than one of the above is correct.

Question 22

Many cars are now equipped with anti-lock brakes

(ABS), which prevents locking of the wheels during

emergency braking. What is the main advantage?

a) This saves the tires. Otherwise too much rubber is

left on the road.

b) Provides more control over the car but stopping dis-

tance increases slightly.

c) This leads to a shorter stopping distance because

tires exert rolling friction which is larger than kinetic

friction.

d) This leads to a shorter stopping distance because

tires exert rolling friction which is larger than static

friction.

e) This leads to a shorter stopping distance because

tires exert static friction which is larger than kinetic

friction.

Question 23

Rank in order, from brightest to dimmest, the identical

bulbs A to D.

a) A = B = C = D.

b) A = B > C = D.

c) A > C > B > D.

d) A > C = D > B.

e) C = D > B = A.

Part B: Problems

Problem 1

Last year, a customer tried to compare two cars. A

manufacturer of the USA car claims fuel efficiency of

30 mpg (miles per gallon). The manufacturer of the

European car states the fuel efficiency of 7.8 l/100km

(liters per hundred kilometers).

(a) Which car is more efficient and by how much?

This year, still undecided, this customer noticed that

both manufacturers improved their fuel efficiency num-

bers by 20%.

(b) Which car is more efficient now, and by how

much?

Fig. 1 shows the velocity as a function of time graph

for a trip you took with your car.

Figure 1

(c) Determine the total distance travelled during this

two hour trip.

(d) Fig. 2 displays the air drag force as a function

of velocity. What is the total work done by the drag

force on the car during this two hour trip?

Figure 2

(e) Each liter of gasoline has 35 MJ of energy. The

efficiency of the motor as a function of the car’s speed

is shown on Fig. 3. How much gasoline is used to over-

come the air drag during this two hour trip?

Figure 3

(f) In which part of the trip the fuel was used most

efficiently (least gasoline used per kilometer travelled)?

Problem 2

Photo A shows a pendulum for a grandfather clock. It

consists of very thin sets of iron and zinc rods and the

pendulum bob. At room temperature there is one iron

rod of length L

0Fe

= 68.00 cm , two iron rods of length

L

1Fe

and two zinc rods of length L

Zn

connected as in

diagram B. Both sets of rods are of negligible weight

compared to the pendulum bob. The thickness of the

connecting pieces is negligible compared to the length

of the rods. The bob is attached to the iron rod. The

pendulum length, then is L = L

0Fe

+ (L

1Fe

− L

Zn

L = 70.00 cm.

(a) Does the position of the rods in diagram B cor-

respond to a warmer day or a colder day compared to

their position in diagram C?

(b) Find L

1Fe

and L

Zn

if the pendulum period does

not change when the temperature changes.