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 direction 3
3
(b)(i) 1. 4.5 ± 0.1 s 1
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/s^{2} 1
2. 9.0 s or e.c.f. from 1 1
(iii) value stated as 45 m/s ± 1 m/s 1
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/kg 1
4
(b) any 2 from:
molecules vibrate
pass energy from molecule to molecule
process is conduction 2
2
3 (a)(i) mass = 0.75 kg 1
(ii) weight =0.75 x 10 1
= 7.5 N 1
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 turn 3
3
(c) use of k.e. = ½ mv^{2} 1
= ½ x 0.5x1.2 ^{2} 1
=0.36 J 1
3
(d) any 2 from; (only) k.e. (before impact)
less or some k.e. after impact
heat + sound 2
2
4 (a) any 2 from:
random
collides with or bounces off sides
hits or bounces off other molecules
other relevant points/explanations 2
2
(b)(i) hits / bounces off ABCD at some time 1
(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 10^{5}) = 2.3 x l0^{5 }Pa 1
2
5 (a) hits at right angles to surface / angle i = 0 ^{o} along normal 1
1
(b) velocity/speed/wavelength 1 increases at F,decreases at D 1
2
(c) correct angle marked / value 45^{o} 2
2
(d) refractive index = 1/sin 45^{o} 1
= 1.4(1) 1
2
6 (a)(i) place of higher pressure / air molecules closer together 1
(ii) place of lower pressure / air molecules further apart 1
2
(b) wavelength = 2.5 m 1
frequency = (330/2.5=) 130 Hz 1
2
(c) distance travelled in 1.2 s = (330 x 1.2 =) 396 m 1
distance = 200 m 1
2
7 (a) circuit with battery symbol and switch 1
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 A 1
2
(c)(i) use of VIt 1
= 19(.2) J 1
(ii) resistance = 1.2/0.4 1
= 3 ohm 1
4
(d) e.m.f. = joules/coulomb 1
= 24/16 or 1.5 V 1
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 A 3
3
9 (a) deviation up marked P 1
deviation down marked R /or opposite way, both marked 1
both correct and reasonable curves 1
3
(b) Any three from:
in front/behind paper / at right angles to electric field 1
Npole “in front” of diagram (to give field into paper) magnetic field deflects beam “downwards”
by Fleming’s rule etc. 2
3
10 (a) ^{228}_{90} Th ^{4}_{2} He + ^{224}_{88} Ra 2 2
(b)(i) must be γ because α and β absorbed by Aluminium /
only γ not absorbed 2
(ii) α / β / γ 1
one reason e.g. range of any/all greater than 1.5 cm in air 1
4
(c)(i) atoms of gas gain / lose electron(s) / by or from colliding particles 1
(ii) (photons) not particles / no mass / no charge / very penetrating /
speed of light etc. 1
energy (of photons) not big enough 1
3
