(a) (i) Stress = force / area C1
force = stress ´ area
= 180 ´ 106 ´ 1.5 ´
10–4
= 27000 (N) A1
(ii) Y M = stress / strain C1
=
180 ´ 106 / 1.2 ´ 10–3 or using the gradient C1
=
1.5 ´ 1011 N m–2 A1
(b) brittle
elastic/
graph shown up to elastic limit
obeys
Hooke’s law / force α extension / stress α strain
no
plastic region B3
MAX
3
[8]
cast iron: brittle
brittle explained as having no plastic region
elastic
elastic explained as returning to original length when
the load is removed / linear graph / Hooke’s law obeyed
or equivalent words MAX 3
brittle explained as having no plastic region
elastic
elastic explained as returning to original length when
the load is removed / linear graph / Hooke’s law obeyed
or equivalent words MAX 3
copper: ductile
ductile explained as can be formed into a wire
initially elastic
plastic where it stretches more and more with little
increase in stress
plastic explained as does not return to its original length
when the load is removed
reference to necking at the end MAX 3
ductile explained as can be formed into a wire
initially elastic
plastic where it stretches more and more with little
increase in stress
plastic explained as does not return to its original length
when the load is removed
reference to necking at the end MAX 3
polythene: easy to deform / deformed with a small force
plastic
ductile
polymeric MAX 2
plastic
ductile
polymeric MAX 2
MAX
8
QWC: spelling, punctuation and grammar B1
organisation and logic B1
organisation and logic B1
[10]
