Mark scheme for IGCSE Physics (0625/3) – Extended Theory November 1999
1
(a)(i)
PE (for one fall) is mgh
= (200 x 10 x 6)
= 12 000 J
(ii)
PE (lost) = KE (on impact) or v = 2gh or s = 2at
12000(J) or answer to (i) = ½ mv or v = 2 x 10 x 6 or t = 1.1 s
v = 120 or v = gt
v = l0.95 or 11 m/s
(b)(i)
(Energy to do) work/mechanical
energy to move the pile against resistance/ground forces
(Energy to) heat
(Energy to) sound (energy chains max 1, first answer only considered.)1
At impact kinetic energy/ momentum large
After impact kinetic energy/ momentum soon zero
Kinetic energy change/ momentum change large
Slows to rest in very short distance/time
KE lost/work = force x distance the pile moves / rate of change of
momentum = force
1
1
1
(c)
lifting suspension etc/ pile deeper after each hit
need more p.e. each time
Rising mass gains k.e.
All lost at top
Power to stop/brake rising mass
All lost as heat
Efficiency of motor not 100%
Lost as heat
1
1
1
1
1
1
1
1
4 (max)
(d)
Greater mass
Fall greater distance
Use motor to drive mass down/thinner or pointed pile
1
1
1
3
(a)
Take temperatures before and after heating/ temperature difference
with thermocouple
Take the time that the heater is switched on/ time with stopwatch
Find in some way the mass of the block and the power of the heater
(ii)
2
1
1
1
1
1
1
1
7
1
1
1
1
2
8 (max)
1
1
2
3 (max)
(b)
Heat input of heater = heat gained by the block
Heat input of heater =200 x 1 50(J)
Heat gained by metal =1 x s x 50(J)
s = 600 (J/kgK)/ 0.6 (J/gE)
1
1
1
1
4
(c)(i)
Outline e.g. 2 metals to suitable meter
Essential parts labelled
Temperature difference produces an emf/voltage/current
emf/current read by meter as a temperature
Temperature rapidly changing/small changes in temperature
1
1
1
1
1
(ii)
(iii)
3
measures high/low/wide range of temperatures
Not fragile like mercury in glass /can be made recording/remote
reading / thermometer not removed
1
(a)
Each reflected angle 85o/10o/170o deviation at each reflection
Total deviation 20o /160o
1
1
2
(b)
(Angle of incidence much) greater than the critical angle
So total internal reflection occurs
1
1
2
(c)(i)
1.50 = 1/sin c
sin c=0.6667
c = 41.8o / 42o
(Angle of incidence is) less than the critical angle
Refracted (out into the air)/ not totally internally reflected
1
1
1
1
1
4 (max)
Light of one colour/ wavelength
Light of one frequency
Speed = 4 x l014 x 5 x l0-7
= 2 x l08(m/s)
Speed in air/ speed in glass = refractive index
Speed in air / speed in glass x 1.50
1
1
1
1
1
1
5 (max)
(ii)
(d)(i)
(ii)
(iii)
4
(a)(i)
Speed of rotation (of the coil/magnet)
is faster
The number of turns on the coil / number of coils (not transformer)
is greater
The strength of the magnet / magnetic field
is stronger
Any other correct factor identified
How factor change relates to the emf
(ii)
The induced emf/current produced by a conductor cutting a
magnetic field
induced emf/current also interacts with the magnetic field
interaction produces a force which slows/opposes the moving conductor
(b)(i)
(ii)
(iii)
(c)(i)
1
6 (max)
1
1
1
1
1
1
1
1
4 (max)
1
1
1
7
Power input = power output / 400 x 80 = 30 000 x I
I = 1.1(A)
Reduce voltage
to value suitable for consumers / 240 V / 110 V
Current in these cables much reduced
(because) voltage increased
Heat = I 2Rt or Power = I2R or heat in cables less
1
1
1
1
1
1
1
6 (max)
3.1 (A) at X
1
(ii)
(iii)
(iv)
(v)
5
(a)
(b)(i)
(ii)
(c)
0.8 (A) at Y
R = 110/any current value
R = (110/0.8) = 138 (ohm)
Any attempt at use of I/R formula for parallel resistors
1/R = 1/24 + 1/48
R = 16 (ohm)
Use of VI or I2R for calculating power
= 110 x 4.6/4.62 x 24
= 506/508 (W)
Use of energy = I 2 Rt / VIt
= 30000 / 31000 (J)
Diagram showing radioactive liquid in pipe, weld and detector in
correct places
three labels
Where weld thin reading rises
Radiation passes more easily through / less absorbed by thinner metal
1
1
1
1
1
1
1
1
1
1
1
10 (max)
1
1
1
1
3 (max)
Alpha - none passes through steel
Beta - some passes through steel
Gamma - most/all passes through steel
Accept either beta or gamma with some reasoning
Beta/gamma with clear reason for the choice
1
1
1
1
1
4 (max)
Any 3 standard precautions which apply to this situation
(generally shielding/absorbing, distance, monitoring radiation)
3
3