1. Edexcel AS Physics Unit 1 : Chapter 7: Solid Materials
Prepared By: Shakil Raiman

2. 7.1 Elastic Deformation
A material undergoing elastic deformation will return to its original dimensions when the deforming force is removed.
Example: Spring, Steel wire etc.

3. 7.2 Plastic Deformation
A material undergoing plastic deformation will not return to its original dimensions or remain deformed when the deforming force is removed.
Example: modelling clay

4. 7.3 Elastic and Plastic Deformation
Some material can behave in an elastic or plastic manner depending on the nature of the deforming force.
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 panels.

5. 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 surface.
Diamond is hardest which has a rating 10.
Stiffness: A stiff material exhibits very small deformations even when subjected to large force.
Steel etc.

6. 7.4 Properties of Solid Materials
Strength: An object is strong if it can withstand a large force before it breaks.
Steel is strong but cotton is weak.
Malleability: A malleable material can be hammered out into thin sheets.
Gold

7. 7.4 Properties of Solid Materials
Ductility: Ductile materials can be drawn into wires.
copper

8. 7.5 Stress
Stress (tensile/compressive stress) is defined as force per unit cross-sectional area.
Unit: Pa (Pascal)

9. 7.6 Strain Strain is defined as extension per unit original length.
Unit: no unit

10. 7.7 Young’s Modulus
Young modulus is defined as the ratio of tensile or compressive stress to strain.
Unit: Pa (Pascal)

11. 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)
where K represents the stiffness or spring constant

12. 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.

13. 7.10-1: Stress-Strain Graph

14. 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.

15. 7.10-3: Stress-Strain Graph
C 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.

16. 7.10-4: Stress-Strain Graph

17. 7.10-5: Stress-Strain Graph

18. 7.10-6: Stress-Strain of Rubber
The hysteresis loop for stress-strain graph represents the energy per unit volume transferred to internal energy during load-unload cycle.

19. Thank You All
Wish you all very good luck and excellent result.