#3.2a(i)
simple mechanical behaviour: elastic and plastic deformation and fracture
#3.2a(ii)
direct evidence of the size of particles and their spacing
Examples: Scanning Tunnelling Microscope images; Rayleigh’s oil drop experiment
#3.2a(iii)
behaviour/structure of classes of materials, limited to metals, ceramics and polymers; dislocations leading to slip in metals with brittle materials not having mobile dislocations; polymer behaviour in terms of chain entanglement/unravelling
#3.2a(iv)
one method of measuring Young modulus and fracture stress.
#3.2b
Make appropriate use of:
(i) the terms: stress, strain, Young modulus, tension, compression, fracture stress and yield stress, stiff, elastic, plastic, ductile, hard, brittle, tough, strong, dislocation
by sketching and interpreting:
(ii) force–extension and stress–strain graphs up to fracture
(iii) tables and diagrams comparing materials by properties
(iv) images showing structures of materials.
#3.2c(i)
Hooke’s Law, \(F = kx\);
energy stored in an elastic material (elastic strain energy) = \(\dfrac{1}{2}kx^2 \);
energy as area under Force–extension graph for elastic materials
(loading only)
#3.2c(ii)
\(\text{stress} = \dfrac{\text{tension}}{\text{cross-sectional area}}\),
\(\text{strain} = \dfrac{\text{extension}}{\text{original length}}\),
Young modulus \(E = \dfrac{\text{stress}}{\text{strain}}\)
#3.2d(i)
plotting force–extension characteristics for arrangements of springs, rubber bands, polythene strips, etc.
links to 3.2a(iii), b(ii), c(i), PAG2
#3.2d(ii)
determining Young modulus for a metal such as copper, steel or other wire.
links to 3.2a(iv), c(ii), PAG2