Elastic vs. Plastic Deformation in Rubber Bands

Steps:

• Elastic deformation returns the material to original shape upon force removal, storing work as elastic potential energy.
• Plastic deformation causes permanent shape change, as atomic bonds break and reform in new positions.
• For rubber bands, stretching can be elastic (reversible) or plastic (irreversible) depending on force magnitude.
• Removing force after plastic stretch leaves residual extension, distinguishing it from elastic behavior.

Why D is correct:

• Plastic deformation, by definition, results in permanent strain, so the length remains greater than original after unloading.

Why the others are wrong:

• A: Elastic stretching stores work as potential energy, recoverable upon unloading, not fully converted to thermal energy.
• B: Elastic deformation is reversible but not always linear, so it does not necessarily obey Hooke's law (F = kx).
• C: The gradient (slope) represents stiffness or Young's modulus in the elastic region, not plastic where behavior is nonlinear.

Final answer: D