elastic properties of solids

About elastic properties of solids

1. -Elastic Properties of Solids -Elastic Properties of Solids
AP Physics C
Mrs. Coyle

2. •Real objects are not rigid but can deform
under the influence of an external force.
•Remember: Hooke’s Law F=-kx

3. Elastic Properties of SolidsElastic Properties of Solids
•Length (Tensile Stress- Strain)
•Shape (Shear Stress-Strain)
•Volume (Bulk Stress-Strain)

4. Elasticity of Length- CharacteristicsElasticity of Length- Characteristics
•Tensile Strain=
L
L
D
Tensile
Stress=F/A

5. Elasticity in LengthElasticity in Length
• Tensile Stress = Y x Tensile Strain
•Y is known as Young’s Modulus
•Units of Y are N/m
2
F L
Y
A L
D
=

6. Tensile Strength
Test
•Tensile Strength
Sample

8. Ex: #30
•A steel wire of diameter 1mm can
support a tension of 0.2kN. A cable to
support a tension of 20kN should have a
diameter of what order of magnitude?
•Ans: 1cm

9. Elasticity in Shape - Shear Stress= F / A

10. Example: Shear Stress
http://www.fema.gov/plan/prevent/earthquake/fema74/chapter2_2.shtm

11. http://www.fema.gov/plan/prevent/earthquake/fema74/chapter2_2.shtm

12. Shear Stress and Shear StrainShear Stress and Shear Strain
F x
S
A h
D
=
S is the Shear
Modulus,
Unit : N/m
2

13. Ex: #33
If the shear stress in steel exceeds 4.00x10
8
N/m
2

the steel ruptures.
a)Determine the shearing force necessary to shear a
steel bolt 1.00cm in diameter.
Ans: a) 3.14x10
4
N

14. Ex: #33 cont’d
b)Determine the shearing force necessary punch
a 1.00cm diameter hole in a steel plate
0.500cm thick.
Ans: b) 6.28x10
4
N

15. Elasticity in VolumeElasticity in Volume
F V
B
A V
D D
=-
B is the Bulk
Modulus
Unit: N/m
2

16. •Note that ΔF/A is pressure.

17. Ex:#35
When water freezes, it expands by about 9%.
What pressure increase would occur inside
your automobile engine block if the water in it
froze?
(The bulk modulus of ice is 2.00x10
9
N/m
2
)
Ans: 1.65 x 10
8
N/m
2

18. Explaining the inertia ball tensions.

19. •How is ΔL affected
when you have
two same springs
in series or in
parallel pulled by
the same force?