2

SECTION A

Answer ALL questions.

You MUST write your answers in the spaces rovided1 this answer booklet.

I, (a) Figure 1 shows a skydiver ofn1s m fa1lig under the influenr of avi and a dragforce F1 that is proportional to c by”). ‘hre v is the ve1octy of the skydiver as shefaLls, h is a constant and n is ab integer.

\t

Figure 1

(i) Next to Figure 1 draw a free body diaam to show the forces acting on the sky-diver, [ I mark I

(ii) Inshow tha he er doward acceleration is a, the equation of motion forthe skydiver can ‘ritten as

g-a— v”.In

./1

t’JLt

* b V VV\CX.

rVtC

I

F2mrks!.v

;J \,

r•.

i

TABLE 1

h

C +4/X

3 niarksj(iv) &ulculate the terminal velocity of a skydiver with a .mass of 785 k, given that

bO25i kgrn1.

a 2

a-

V

- 3

a - -t-V

3rn.aril

C) ( .N 1) ••i•••• H F )EFT PA

Ib) Table I shows (iatacrded .ft th acceleration and veioctty of theunderwent free faW.

I

Acceler4tion eIontyv/ms’

skydiver as she

g—a/1ns Ig i’

1 a___ z2±Di_891 15 QO LQD824 20j I36 25

62 S 30O1LL5 1i/

/(i) Complete Table 1 by tilling in the blank columns. f 3 marks

(ii) Onpage4,plotaaphoflgg—a)vslgv. — 1 3 rnarks}(iii) Calculate the gradient ot the graph and hence determine a value fbr i (to the

nearest integer),

t)

(,, N) (I3

-veJ .- —

-3 -o oq

z. ).

•1 •.-

a— —

•- —I va

CAPE PHYSICS 2011Paper 02 - UNIT 1 EXEMPI.ARS

MODULE 1

Question 1

The candidate demonstrated sound knowledge and understanding of the material presented in thisquestion.

In parts (a> and (b), the candidate correctly drew the free body diagram showing the forces acting on theskydiver and was then able to use the information provided to derive the force equation required forthe proof.

In part (b) (i), the candidate showed a good grasp of the use of significant figures and correctlycompleted each of the three columns of the table provided.

With respect to the graph, the candidate correctly deduced ‘n’ as the gradient value and displayed theunderstanding that an integer does not require decimal places. However, it must be pointed out that the‘broken axis’ symbol, as used by the candidate in drawing the graph, is inappropriate in Physics.

In part (b) (iv), although it was not explicitly stated in the response that a = 0, the candidate used thefact that at terminal velocity the upward forces = downward forces to obtain the correct value.

-7—

2. (a) Figure 2 shows a loudspeaker sounding a constant note placed aboxe a long ertical tubecontaining water which slowly runs out at the lower end.

Figure 2

(i) I)escribe arid explain what is heard at a certain level as the water runs out at thelower end.

-—-

S2’

- 1’ - — ‘- -: •--—

iTb. [he frequency of a ibratin string s given by J , .here Tis the tension in the

J\p

string, p is the mass per unit length of the string and 1 is the length of the string.

While the tension of a vibrating string was kept constant at 100 N, its length was varied

in order to tune the string to a series of tuning forks. The results obtained are shou n inTable 2.

TABLE 2

Frequency of Fork,f256 288 P_0 384 450 5121

(Hz)

: Length of String,!0.781 0.695 0.625 1 0.521 0.444 0.391

!(in) I

(iv) Calculate the gradient of the graph.

2

.1 O x 2v2.

ul.O %,

tz

iDetermine value othe mass

r

( .l.

.i. - I_.

per unlt ienuth,

(i)

(ii)

(ili)

Complete the table by filling in the values for 1/1, ( 1 mark IOn page 9, plot a graph of frequencyfvs 1/1. 1 3 marksl

Use the graph to determine the frequency of an unmarked fork which was in tunewith 11,7 cm of the sthng.

-

m- —--- \ .--..!.. .,. —L tk .1 ç 0. ‘-j .

ori 2.40

_________________

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•ça_ ‘-\ ij()

2 marksl

I

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600

550

500

$50

300

30

-9-

s

I

I( I’, k

CAPE PHYSICS 2011Paper 02 - UNIT 1 EXEMPLARS

MODULE 2

Question 2

This script represented an outstanding response to the question.

In part (a), the candidate was able to correctly describe and explain the loud sound heard at a certainlevel in terms of the wavelength of the sound compared to the length of the air column above the watersurface in the tube (1 =

In part (b), 1/I was found correctly to three significant figures and the graph off vs 1/1 was accuratelyplotted. The frequency of the unmarked fork was correctly determined by first finding 1/1 when

4L7 cm and using the value to deduce the corresponding frequency of f = 480 Hz from the bestfit line.

In part (b) (iv>, the candidate calculated the gradient by using the large triangle on the graph anddividing the vertical change in frequency by the corresponding horizontal change in 1/1 using theform u I a

y x vertical axis scale

x x horizontal axis scale

in which x and y represented the number of units along the horizontal and vertical lengths respectivelyof the gradient triangle. Many of the other candidates who correctly calculated the gradient used themore popularm = Y2—Y1

formula.x2 — x1

Finally, the candidate also correctly determined the value of mass per unit length, j, using the gradient

found in part (i) and then equated the gradient to to solve for .

-iN-

6. 1 do e clnxws or w as coo amed in a \ I tdcr xdo piston 1 th. ta! qtn M mn at a tenlcrattne or I K I he cx Iinder — thermally isolated from lb surroundings. inn the \

It ISI Not I0n in Nfrss ri 103 1 Pt

Figure 3

J hernialinsulator

I) F I e mu tar It state or an i leal pis i find tim ito it n it Its

10) TI a s is hen ompres d to 3.5 10 ad nd te ope tnt is to 7s r SC a cit r rattue

.i n 5riaroseop1e NLJIC tNt ‘g hrs lao if therm xl: a tina. I marks

t) on a ni1croeonte seaL. UNIOC the knjte theor’ ti taes. 1 3 marksl

) ( [cal te IC Ott Sn ‘of tie as a er ti act pr hr 2 rnarksj

a! I he xx ork done on the paN donna the compression i xfl J I e Inc lit st late ot thenouds ii trnics:o find tdo increase in the iota ‘ml ‘ncr of the cas d liii.’ he eoO’p ‘sslOn.

1 1 it rk I

I martaj

I dal IS marks

to n U ‘i Id.t

1 3 marks

I) K F plar

taic:iate he nmlar h.-t e tpaeit\ ito the nis 5 tfl e,0rlItler

19

‘kOu MUST write the answer to Question 6 here.

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a i

3

(b)

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a•

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CAPE PHYSICS 2011Paper 02 - UNIT 1 EXEMPLARS

MODULE 3

Question 6

The candidate demonstrated sound understanding of the thermal properties of matter. In part (a), thecandidate selected the correct equation, made the correct substitutions and provided the answercorrect to three significant figures.

In explaining the rise in temperature in part b (i), the candidate first defined the first law ofthermodynamics and each of the associated terms. The candidate correctly indicated that work is beingdone on the gas and that this leads to an increase in the internal energy and an increase in temperature.However the candidate failed to indicate that because the cylinder is thermally insulated Q = 0 and soall the work done goes into increasing the internal energy.

In part (b) (ii), the candidate accurately explained that as the piston moves in, it hits the molecules whichrebound with greater speed thus increasing their kinetic energy and resulting in the increase intemperature.

P1V1 P21’2The candidate correctly used the equation = in the calculation for part (c). However, in

T1this case, the equation P V = n R T could also have been used.

In parts (d) and (e), the candidate again used the proper substitutions and correctly manipulated theequations to find the increase in the internal energy of the gas and the molar heat capacity of the gas.

It should also be noted that the candidate consistently calculated all answers in parts (a), (c) and (e) tothree significant figures.