-Elastic Properties of Solids

# -Elastic Properties of Solids

## -Elastic Properties of Solids

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1. -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 Solids • Length (Tensile Stress- Strain) • Shape (Shear Stress-Strain) • Volume (Bulk Stress-Strain)

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

5. Elasticity in Length • Tensile Stress = Y x Tensile Strain • Y is known as Young’s Modulus • Units of Y are N/m2

6. Tensile Strength Test • Tensile Strength Sample

7. 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

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

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

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

11. Shear Stress and Shear Strain S is the Shear Modulus, Unit : N/m2

12. Ex: #33 If the shear stress in steel exceeds 4.00x108 N/m2 the steel ruptures. a)Determine the shearing force necessary to shear a steel bolt 1.00cm in diameter. Ans: a) 3.14x104 N

13. 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) 6.28x104 N

14. Elasticity in Volume B is the Bulk Modulus Unit: N/m2

15. Note that ΔF/A is pressure.

16. 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 2.00x109 N/m2 ) Ans: 1.65 x 108 N/m2

17. Explaining the inertia ball tensions.

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