How The Bruh Moment Changed History - English - Essay

1
Exam Choice
2009 Physics Preliminary Examination. Marking Guidelines and model Answers.
Part A Multiple Choice
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
A C D C B C A D A B B B A C D
Part B
16 a.
Marking Criteria Marks
Sufficient apparatus sketched and labelled so that investigation could be performed properly 2
Some appropriate parts of the investigation sketched and/or labelled 1
e.g. (note that question only asks for the sketch of apparatus)
nodes where open-ended glass tube speaker signal
particles settle with fine sand/powder generator
which collects at the nodes
16 b.
Marking Criteria Marks
Complete relationship described 2
Relationship described in a simplistic manner 1
The frequency is inversely proportional to the wavelength OR the product of the frequency and wavelength is constant.
17
Marking Criteria Marks
 Full description given with similarity to fibre optic described fully;
 useful diagram included and referred to
3
Method of conveying sound in pipe described 2
Method of conveying sound in pipe identified 1
The sound waves reflect off the walls of the pipe and continue to travel down the pipe, “trapped”. Light undergoes total internal reflection in
an optical fibre in a similar fashion – “trapped” in the fibre.
18 a.
Marking Criteria Marks
Both a carrier wave and AM modulation correctly depicted 2
Either a carrier wave OR a form of modulation is depicted 1
Radio waves have a much higher frequency than human hearing so cannot be converted directly into sound for the communication of voice
or music. By superposing the actual communication signal onto the carrier wave, the message etc can be decoded back into sound that
humans can hear by the radio receiver, thus enabking long distance transmission and reception of communication.
19
Marking Criteria Marks
Correct equations used to find correct values and an average taken correctly to 2dp 4
Correct refractive indices found for three instances 3
Correct refractive index calculated for one instance 2
Snell’s law identified to attempt to find refractive index OR an average of incorrect values attempted 1
sin
n
sin
sin60
sin 45
1.2247
o
o
i
r



sin
n
sin
sin 45
sin34
1.2645
o
o
i
r



sin
n
sin
sin30
sin 23
1.2797
o
o
i
r



2
 1.2247 1.2645 1.2797 3
1.26
. . n=1.26
average
i e
   

20 a.
Marking Criteria Marks
Correct answer with correct number of significant figures 2
Correct equation used with subsequent incorrect substitution but answered with correct number of sig
figs OR correct answer with incorrect number of significant figures
1
4
8
3 -1 -1
1.5 10 N
5.0 10 C
3.0 10 N C (or V m )
F
E
q






 
20 b.
Marking Criteria Marks
Complete answer provided to find mass 2
An aspect identified, e.g. acceleration measured 1
Observation and measurement of the particle’s acceleration, then use m=F/a to find the mass of the particle.
21 a.
Marking Criteria Marks
Two reasons identified 2
One reason identified 1
e.g. To allow wires of appropri...