Young Modulus
Physics: AQA A Level, topic 4.2.4
The Young Modulus
Stress and strain can be combined to give a property of a material. This property of the material is called the Young modulus and it is the same for any sample of the material; it does not depend on the size or shape of the sample.
Young modulus
- Young modulus gets it name from the scientist Thomas Young.
- It is defined as the ratio of stress to strain.
- The Young modulus can be written as:
- Young modulus
Stiffness of a material
- The Young modulus represents the stiffness of a material.
- Stiff materials have a small strain for large stresses.
Gradient and Young modulus
- The gradient of the linear section of a stress-strain graph is the Young modulus.
Determining the Young Modulus
The Young modulus can be determined simply. The simple method involves stretching a long thin wire and recording the stress and strain.
Equipment
- Set up your equipment as shown.
Method
- Determine the cross-sectional area of the wire by assuming a circular cross section.
- A micrometer screw gauge would be the best piece of equipment to use here.
- Determine the un-stretched length of the wire.
- Add masses and record the extension of the wire. You can work out the applied force from the masses added.
- For each set of masses added, you can obtain pairs of stress-strain values.
Result
- The gradient of the linear section of a stress-strain graph is the Young modulus.
Test yourself on Young Modulus
Which statements about Young's modulus are true?
What is the correct form of the Young's modulus equation?