Which of the following statements best describes a rigid body? A body which

Analyze the question: We need the statement that best describes a rigid body.

Concept: In physics, a rigid body is an idealized solid in which the distance between any two points stays constant. It does not change shape or size when forces act on it. In other words, it does not deform, or its deformation is negligible.

Checking each option:

• A. is not equally deformed: This is the key's choice, but it is awkwardly worded and does not match the textbook definition. It could be read as "does not get deformed equally", meaning that it doesn't deform the same way throughout. That is a stretch, but it is the closest to "not deformed" among the options.
• B. when deformed regains its shape: This describes an elastic body, not a rigid one.
• C. is brittle: A brittle material breaks suddenly without much plastic deformation. This is a different property, and brittle objects are not necessarily rigid in the ideal sense.
• D. when deformed remains deformed: This describes a plastic body.

Conclusion: B and D describe elastic and plastic behaviour, and C describes brittleness, so none of them defines rigidity. The only option that points toward the idea that a rigid body's points do not shift relative to each other, so it does not undergo deformation, is A.

Exam tip: Remember the three keywords:

• Elastic → regains shape
• Plastic → stays deformed
• Rigid → does not deform (ideal)

When a question is poorly worded, eliminate the options that clearly describe other properties. Whatever remains is likely the answer.