Answers to KS3 level 8 questions

39.     (a)     300 C                                                unit required for the mark                        1

accept ‘5.0 × 60 C’

(b)     (i)      48                                        unit required for the mark                        1

accept ‘240/5 ’

(ii)     1200 W or 1.2 kW                    unit required for the mark                        1

accept ‘240 × 5 W’

(c)     (i)      600 J                                        unit required for the mark                        1

accept ‘J/s’ or ‘W’

accept answer to (b) (ii) × 0.5 J

(ii)     5 kg                                         unit required for the mark                        1

consequential marking applies in this
part of the question

accept ‘kg/s’

accept answer to (c) (i) ¸ 120 kg

[5]

40.     (a)     25,000 m2 or 0.025 km2                      unit required for the mark                               1

accept ‘500 000 ¸ 6 × 0.3 m2

(b)     (i)      it cannot meet winter requirement                                                              1

(ii)     any  one from                                                                                           1

·   variable output or output depends on the weather

·   unsightly or noise pollution

·   output cannot be increased to cope with future growth in demand

accept ‘it isn’t always windy’

accept ‘interference with TV and radio signals’

[3]

41.     (a)     any two from                                                                                                     2

·   molecules move faster as they fall inwards or PE  is transformed into KE

·   collisions between the molecules make their motion random or KE is transformed into thermal energy

·   higher speed and random motion means higher temperature

accept ‘collisions produce heat’

(b)     any one from                                                                                                     1

·   the pressure of the hot gas             accept ‘collisions between gas molecules’
at the centre

·   the angular momentum or              accept ‘radiation pressure’
rotation or spin of the cloud

(c)     radiation                                            accept ‘radiation and convection’           1
or convection through the cloud          for one mark

radiation from the cloud into space                                                                       1

(d)     any one from                                                                                                     1

·   it is not bright enough

·   there is not enough radiation

·   not enough energy is transferred

·   radiation is absorbed by dust

(e)     hydrogen                                                                                                            1

(f)      smaller nuclei join to make                  accept ‘nuclei join together’ or ‘hydrogen   1
bigger nuclei                                      nuclei join to make helium’

do not accept  ‘hydrogen burns’

[8]

42.     (a)     bulb flashes on or glows briefly           do not accept ‘bulb turns on’ without       1
                                                         reference to ‘for a short time’

 any two from                                                                                                    2

·   primary current or magnetic flux chances

·   a voltage is induced across the secondary or a current is induced in the secondary

·   no induced voltage when flux reaches a steady value

accept ‘voltage across primary changes’ or ‘field through secondary grows’

accept ‘no induced current when primary current stops changing’

award one mark for ‘nothing happens’ with the explanation ‘transformers do not work on dc’

award all three marks for ‘nothing happens’ with the explanation ‘magnetic field builds up too slowly so induced voltage is too small to light the lamp’

(b)     bulb stays off                                     accept ‘nothing’                                       1

the magnetic field does not change                                                                      1

(c)     bulb flashes on or glows briefly           do not accept  ‘bulb turns on’ without      1
                                                         reference to ‘for a short time’

do not accept  ‘bulb turns off or goes out’

(d)     C                                                    if more than one box is ticked                  1
                                                         award no mark

[7]

43.     (a)     (i)      0.5 or 0.5 s                              accept ‘0.49’                                            1

(ii)     2.5 m/s or  21/2 m/s                                                                                   1

(iii)     1.25 m or 11/4  m                      consequential marking applies in this part   1

accept answer to (a) (i) × answer to (a) (ii) unit required for the mark

accept ‘5 /4   m’ or ‘1 /2  × 0.5 × 5 m’

(b)     (i)      any one from                                                                                            1

·   it is bouncing                        accept ‘hitting the floor and bouncing’

·   it is in contact with the          accept ‘hitting or touching the floor’
floor                       &nb