5.3.1 Changing Shape

• What occurs when a force is applied to an object?

  Deformation occurs, causing the object to change shape.
• What are the two types of deformation?

  • Elastic Deformation: Returns to original shape after force removal.
  • Plastic Deformation: Does not return to original shape after force removal.
• What is the definition of elastic deformation?

  Elastic deformation is when the object returns to its original shape and size once the force is removed.
• Give an example of elastic deformation.


  Stretching a rubber band, which returns to its original length when the force is removed.
• What is the definition of plastic deformation?

  Plastic deformation is when the object does not return to its original shape after the force is removed, resulting in a permanent change.
• Provide an example of plastic deformation.


  Bending a paperclip, which remains in its new shape even after the force is removed.
• What are the characteristics of elastic and plastic behavior in materials?

  • Elastic Behavior: Materials return to original shape after deformation; described by Hooke's Law.
  • Plastic Behavior: Materials permanently deform; important in processes like metal forming and shaping.
• What does Hooke's Law state?

  Hooke's Law states that the force needed to extend or compress a spring is proportional to the distance it is stretched or compressed, as long as the elastic limit is not exceeded.
• What is the formula for Hooke's Law?


  F = k × x
• What does the variable F represent in Hooke's Law?

  F represents the force applied (in Newtons, N).
• What does the variable k represent in Hooke's Law?


  k represents the spring constant (in Newtons per meter, N/m).
• What does the variable x represent in Hooke's Law?

  x represents the extension or compression from the natural length (in meters, m).
• What does a higher spring constant indicate?

  A higher spring constant indicates a stiffer spring that requires more force to stretch or compress.
• What is elastic potential energy?

  Elastic potential energy is stored in an object when it is deformed elastically.
• What is the formula for elastic potential energy?

  Elastic Potential Energy (E) = 1/2 k x²
• What does the variable E represent in the elastic potential energy formula?

  E represents the elastic potential energy (in Joules, J).
• What does the variable k represent in the elastic potential energy formula?

  k represents the spring constant (in N/m).
• What does the variable x represent in the elastic potential energy formula?

  x represents the extension or compression (in meters, m).
• What is the limit of proportionality?

  The limit of proportionality is the point at which Hooke’s Law no longer applies and the material starts to deform plastically.
• How is the limit of proportionality represented graphically?

  In a force-extension graph, the limit of proportionality is where the straight-line portion of the graph curves.
• What is Young’s Modulus?

  Young’s Modulus is a measure of the stiffness of a material, defined as the ratio of stress to strain.
• What is the formula for Young’s Modulus?

  Young’s Modulus (E) = Stress / Strain
• What does stress represent in the context of Young’s Modulus?


  Stress is the force per unit area (in Pascals, Pa).
• What does strain represent in the context of Young’s Modulus?

  Strain is the extension per unit length and is dimensionless.
• What is the formula for calculating stress?

  Stress = Force / Area
• What does the variable Force represent in the stress formula?

  Force is in Newtons (N).
• What does the variable Area represent in the stress formula?

  Area is in square meters (m²).
• What is the formula for calculating strain?

  Strain = Extension / Original Length
• What does the variable Extension represent in the strain formula?

  Extension is the change in length of the material (in meters, m).
• What does the variable Original Length represent in the strain formula?

  Original Length is the initial length of the material (in meters, m).
• What are some practical applications of understanding deformation?

  • Engineering: Designing materials and structures that can withstand specific forces without permanent deformation.
  • Everyday Items: Understanding how items like springs, elastic bands, and flexible materials work.
• What is the summary of deformation and related concepts?

  • Deformation: Change in shape due to applied forces; can be elastic (temporary) or plastic (permanent).
  • Hooke’s Law: F = k × x, applicable for elastic deformation.
  • Elastic Potential Energy: E = 1/2 k x², stored in deformed materials.
  • Young’s Modulus: Ratio of stress to strain, indicating material stiffness.