Overview
This lesson explains the difference between elastic and inelastic deformation, how to calculate the force needed to stretch or compress an object, and the energy transfers in elastic materials.
Elastic and Inelastic Deformation
- Elastic materials return to their original length or shape after the forces are removed.
- Elastic deformation refers to changes in shape or length that are fully reversible.
- Inelastic materials do not return to their original length or shape after the forces are removed.
- Inelastic deformation is a permanent change in an object's length or shape after the force is removed.
Forces and Deformation
- Balanced forces of equal magnitude but opposite direction are required to stretch, compress, or bend an object.
- More than one force must be applied to change an object's length or shape.
- A single unbalanced force will cause the object to move, not deform.
Calculating Force for Stretching or Compressing
- The equation for force: Force (N) = Spring Constant (N/m) × Extension (m).
- You need to memorize this equation for exams as it is not provided.
- The equation also applies to compression, where extension refers to the change in length due to squeezing.
Energy Transfers in Elastic Materials
- When an elastic object is stretched, compressed, or bent, work is done on the object.
- The energy transferred is stored as elastic potential energy, provided there is no inelastic deformation.
- The work done equals the elastic potential energy stored in the object.
Key Terms & Definitions
- Elastic Deformation — Temporary change in shape or length; object returns to original form when force is removed.
- Inelastic Deformation — Permanent change in shape or length; object does not return to original form after force is removed.
- Spring Constant (k) — A measure of a spring’s stiffness, measured in Newtons per meter (N/m).
- Elastic Potential Energy — Energy stored when an object is stretched, compressed, or bent.
Action Items / Next Steps
- Memorize the force equation: Force = Spring Constant × Extension.
- Review the topic of elastic potential energy.
- Prepare for the next lesson on the practical experiment with stretching a spring.
- Practice questions on forces and elasticity from the revision workbook.