Answer: <u>elastically</u> deformed or <u>non-permanently</u> deformed
Explanation:
According to classical mechanics, there are two types of deformations:
-Plastic deformation (also called irreversible or permanent deformation), in which the material does not return to its original form after removing the applied force, therefore it is said that the material was permanently deformed.
This is because the material undergoes irreversible thermodynamic changes while it is subjected to the applied forces.
-Elastic deformation (also called reversible or non-permanent deformation), in which the material returns to its original shape after removing the applied force that caused the deformation.
In this case t<u>he material also undergoes thermodynamic changes, but these are reversible, causing an increase in its internal energy by transforming it into elastic potential energy.</u>
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Therefore, the situation described in the question is related to elastic deformation.
A) Pure substances, Chemical changes
A, B, and C are all incorrect because they are talking about springs. I'm assuming you're talking about a 2 dimensional, side to side pendulum. In that case, the answer is D because as the pendulum goes up from one side, gravity accelerates it downward until it swings to the other side. If you're not talking about this type of pendulum, leave a comment and ill come back.
