Mark scheme for IGCSE Physics (0625/3) – Extended Theory May/June 2000
1(a)Any three from:
velocity is a vector and speed is a scalar
vector or velocity has direction
scalar or speed has no direction or only magnitude
ref to vertical path as fixed direction3
3
(b)(i)1. 4.5 ± 0.1 s1
2. any four from:
decelerates
uniformly
from high velocity at 0 s
to zero velocity(at 4.5 s)
accelerates (for the last 0.5 s)4
(ii)1. (—)10 m/s21
2. 9.0 sor e.c.f. from 11
(iii) value stated as 45 m/s ± 1 m/s1
8
2(a)specific latent heat = heat supplied/mass melted 1
(mass melted =) 0.18 kg 1
(heat supplied =) 60 000 J 1
specific latent heat = 330 000 J/kg1
4
(b)any 2 from:
molecules vibrate
pass energy from molecule to molecule
process is conduction2
2
3(a)(i)mass = 0.75 kg1
(ii) weight =0.75 x 10 1
= 7.5 N1
3
(b)Any 3 from:
(sum of) clockwise moments = (sum of) anticlockwise
moments about pivot
no net turning effect
needs extra moment (one side) to turn3
3
(c)use of k.e. = ½ mv21
= ½ x 0.5x1.2 21
=0.36 J1
3
(d)any 2 from; (only) k.e. (before impact)
less or some k.e. after impact
heat + sound2
2
4(a)any 2 from:
random
collides with or bounces off sides
hits or bounces off other molecules
other relevant points/explanations2
2
(b)(i) hits / bounces off ABCD at some time1
(ii) hits / bounces off all sides at some time / chance of hitting all sides
equal (so equal pressure)1
2
(c)use of p.v = c 1
p = (0.09/0.04 x 105) = 2.3 x l05 Pa1
2
5(a)hits at right angles to surface / angle i = 0 o along normal1
1
(b)velocity/speed/wavelength 1 increases at F,decreases at D 1
2
(c)correct angle marked / value 45o2
2
(d)refractive index = 1/sin 45o1
= 1.4(1)1
2
6(a)(i)place of higher pressure / air molecules closer together1
(ii) place of lower pressure / air molecules further apart1
2
(b)wavelength = 2.5 m 1
frequency = (330/2.5=) 130 Hz1
2
(c)distance travelled in 1.2 s = (330 x 1.2 =) 396 m 1
distance = 200 m1
2
7(a)circuit with battery symbol and switch1
and three from:
at least one straight line inside the coil
at least one loop at each side
at least one complete loop through the coil 2
full field
arrows correct 3
4
(b) use of charge/time 1
= 0.4 A1
2
(c)(i) use of VIt 1
= 19(.2) J1
(ii) resistance = 1.2/0.4 1
= 3 ohm 1
4
(d)e.m.f. = joules/coulomb 1
= 24/16 or 1.5 V1
2
8(a)any 3 from: primary (current) creates magnetic field
field is (constantly) changing
field in core links into secondary
changing field in or through secondary coil
induces a.c. in secondary coil,3
3
(b)VpIp = VsIs
240 x Ip = 12 x 3.2
Ip (= 3.2/20) = 0.16 A3
3
9(a)deviation up marked P1
deviation down marked R /or opposite way, both marked1
both correct and reasonable curves1
3
(b)Any three from:
in front/behind paper / at right angles to electric field 1
N-pole “in front” of diagram (to give field into paper) magnetic field deflects beam “downwards”
by Fleming’s rule etc.2
3
10(a)22890 Th 42 He + 22488 Ra2 2
(b)(i)must be γ because α and β absorbed by Aluminium /
only γ not absorbed 2
(ii)α / β / γ1
one reason e.g. range of any/all greater than 1.5 cm in air1
4
(c)(i) atoms of gas gain / lose electron(s) / by or from colliding particles1
(ii) (photons) not particles / no mass / no charge / very penetrating /
speed of light etc.1
energy (of photons) not big enough1
3
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