AS Unit 1 Topic 7

Edexcel AS Physics
Unit 1 : Chapter 7: Solid Materials
Prepared By: Shakil Raiman
7.1 Elastic Deformation
material undergoing elastic
deformation will return to its original
dimensions when the deforming force
is removed.
 Example: Spring, Steel wire etc.
7.2 Plastic Deformation
material undergoing plastic deformation
will not return to its original dimensions or
remain deformed when the deforming
force is removed.
 Example:
modelling clay
7.3 Elastic and Plastic Deformation
Some material can behave in an elastic or plastic
manner depending on the nature of the deforming
A thin steel sheet will deform elastically when
small forces are applied to it, but the huge forces
of a hydraulic press will mould the sheet into car
7.4 Properties of Solid Materials
Hardness: Hardness is a surface
phenomenon. The harder the material, the
more difficult it is to indent or scratch the
 Diamond is hardest which has a rating 10.
 Stiffness: A stiff material exhibits very small
deformations even when subjected to large
 Steel etc.
7.4 Properties of Solid Materials
 Strength:
An object is strong if it can
withstand a large force before it
 Steel
is strong but cotton is weak.
 Malleability:
A malleable material can
be hammered out into thin sheets.
 Gold
7.4 Properties of Solid Materials
 Ductility:
Ductile materials can be
drawn into wires.
7.5 Stress
 Stress
(tensile/compressive stress) is defined as
force per unit cross-sectional area.
stress 
cross _ sec tional _ area
Unit: Pa (Pascal)
7.6 Strain
 Strain
is defined as extension per unit
original length.
strain 
original _ length
Unit: no unit
7.7 Young’s Modulus
 Young
modulus is defined as the ratio of
tensile or compressive stress to strain.
Young _ mod ulus 
E 
 Al
Unit: Pa (Pascal)
7.8 Hooke’s Law
Hooke’s law states that, upto a given load,
the extension of a spring (or wire) is directly
proportional to the force applied to the
spring (or wire)
F  kx
where K represents the stiffness or spring
7.9 Elastic Potential Energy or Elastic
Strain Energy
 The
elastic potential energy or elastic
strain energy is the ability of a
deformed material to do work as it
regains its original dimensions.
W  Fave x
W  Fmax x
7.10-1: Stress-Strain Graph
7.10-2: Stress-Strain Graph
 O-A
represents the Hooke’s Law region.
Strain is proportional to stress up to
this point. The Young modulus of
material can be found directly by
taking the gradient in this section.
 B is the elastic limit. If the stress is
removed below this value, the wire
returns to its original state.
7.10-3: Stress-Strain Graph
is the yield stress. For stresses
greater than this, the material will
become ductile and deform plastically.
 D is the maximum stress that a material
can endure. It is called ultimate tensile
strength (UTS).
 E or F is the breaking point. After E the
wire starts narrowing.
7.10-4: Stress-Strain Graph
7.10-5: Stress-Strain Graph
7.10-6: Stress-Strain of Rubber
The hysteresis
loop for stressstrain graph
represents the
energy per unit
transferred to
internal energy
during loadunload cycle.
Thank You All
Wish you all very good luck and excellent result.