Mark scheme for igcse physics (0625/3) – Extended Theory May/June 2000




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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/s2 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 mv2 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 105) = 2.3 x l05 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 45o 2



2

(d) refractive index = 1/sin 45o 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

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 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







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