Mark scheme for IGCSE Physics (0625/3) – Extended Theory November 1999

1(a)(i)PE (for one fall) is mgh1

= (200 x 10 x 6)1
= 12 000 J1

(ii)PE (lost) = KE (on impact) or v = 2gh or s = 2at1
12000(J) or answer to (i) = ½ mv or v = 2 x 10 x 6 or t = 1.1 s1
v = 120 or v = gt1
v = l0.95 or 11 m/s1

7

(b)(i)(Energy to do) work/mechanical 1

energy to move the pile against resistance/ground forces1
(Energy to) heat1
(Energy to) sound (energy chains max 1, first answer only considered.)1
(ii)At impact kinetic energy/ momentum large1
After impact kinetic energy/ momentum soon zero1
Kinetic energy change/ momentum change large1
Slows to rest in very short distance/time1
KE lost/work = force x distance the pile moves / rate of change of

momentum = force2

8 (max)

(c)lifting suspension etc/ pile deeper after each hit1

need more p.e. each time1
Rising mass gains k.e.1
All lost at top1
Power to stop/brake rising mass1
All lost as heat1
Efficiency of motor not 100%1
Lost as heat1

4(max)

(d)Greater mass1

Fall greater distance1

Use motor to drive mass down/thinner or pointed pile1

3

2(a) Take temperatures before and after heating/ temperature difference

with thermocouple1

Take the time that the heater is switched on/ time with stopwatch1
Find in some way the mass of the block and the power of the heater2

3 (max)

(b) Heat input of heater = heat gained by the block1

Heat input of heater =200 x 1 50(J)1
Heat gained by metal =1 x s x 50(J)1
s = 600 (J/kgK)/ 0.6 (J/gE)1

4

(c)(i)Outline e.g. 2 metals to suitable meter1
Essential parts labelled1
(ii)Temperature difference produces an emf/voltage/current1
emf/current read by meter as a temperature1

(iii) Temperature rapidly changing/small changes in temperature1
measures high/low/wide range of temperatures1
Not fragile like mercury in glass /can be made recording/remote

reading / thermometer not removed1

6 (max)

3(a) Each reflected angle 85o/10o/170o deviation at each reflection1
Total deviation 20o /160o1

2

(b) (Angle of incidence much) greater than the critical angle1
So total internal reflection occurs1

2

(c)(i)1.50 = 1/sin c1
sin c=0.66671
c = 41.8o / 42o1
(ii)(Angle of incidence is) less than the critical angle1
Refracted (out into the air)/ not totally internally reflected1

4 (max)

(d)(i)Light of one colour/ wavelength1
Light of one frequency1
(ii)Speed = 4 x l014 x 5 x l0-71
= 2 x l08(m/s)1
(iii)Speed in air/ speed in glass = refractive index1
Speed in air / speed in glass x 1.501

5 (max)
4(a)(i)Speed of rotation (of the coil/magnet)1
is faster1
The number of turns on the coil / number of coils (not transformer)1
is greater1
The strength of the magnet / magnetic field1
is stronger1
Any other correct factor identified1
How factor change relates to the emf1

4 (max)

(ii)The induced emf/current produced by a conductor cutting a

magnetic field1
induced emf/current also interacts with the magnetic field1
interaction produces a force which slows/opposes the moving conductor1 7

(b)(i)Power input = power output / 400 x 80 = 30 000 x I1

I = 1.1(A)1
(ii)Reduce voltage1

(iii) to value suitable for consumers / 240 V / 110 V1

Current in these cables much reduced1
(because) voltage increased1
Heat = I 2Rt or Power = I2R or heat in cables less1

6 (max)

(c)(i)3.1 (A) at X1
0.8 (A) at Y1
(ii)R = 110/any current value1
R = (110/0.8) = 138 (ohm)1
(iii)Any attempt at use of I/R formula for parallel resistors1
1/R = 1/24 + 1/481
R = 16 (ohm)1
(iv)Use of VI or I2R for calculating power1
= 110 x 4.6/4.62 x 241
= 506/508 (W)1
(v)Use of energy = I2 Rt / VIt1
= 30000 / 31000 (J)1

10 (max)

5(a)Diagram showing radioactive liquid in pipe, weld and detector in

correct places1
three labels1
Where weld thin reading rises1
Radiation passes more easily through / less absorbed by thinner metal1

3 (max)

(b)(i)Alpha - none passes through steel1

Beta - some passes through steel1
Gamma - most/all passes through steel1
(ii)Accept either beta or gamma with some reasoning1 Beta/gamma with clear reason for the choice 1

4 (max)

(c) Any 3 standard precautions which apply to this situation3
(generally shielding/absorbing, distance, monitoring radiation)3