Materials that can be stretched and still return to their original forms when the stresses are removed are said be

1. Analyze the question The question asks for the term describing materials that are stretched by a stress and then return to their original shape and size once the stress is removed.

2. Explain the concept

• Elasticity is the property of a material to regain its original shape and size after the deforming force (stress) is removed.
• This holds only up to the elastic limit. Beyond that point, the material is permanently deformed.
• Hooke's law applies within this region: F = ke, where the extension is directly proportional to the applied force.

3. Go through the options

• A. Elastic: Correct. This is the exact definition of an elastic material.
• B. Elastomer: This is a specific type of polymer, such as rubber, that shows elastic behaviour. It is a material class, not the general property being described. The question asks for the property, so this is not the best answer.
• C. Plastic: Plastic materials undergo permanent deformation and do not return to their original form. This is the opposite of what is asked.
• D. Thermoplastic: This is a polymer that softens when heated and hardens when cooled. It has nothing to do with recovering shape after stress.

4. Answer The correct option is A. elastic.

5. Tip Remember the pair: Elastic = comes back, Plastic = stays changed. In exam questions, if a material "returns to its original shape after the force is removed," think "elastic" immediately. Also remember that the elastic limit is the maximum stress up to which this behaviour holds.