Impact and Collisions — Behavior of Elastic Bodies When two elastic bodies collide, which of the following occurs during the impact process?

Introduction / Context:
Collision of elastic bodies is described by phases of compression and restitution. Even “rigid” bodies deform locally at the contact region; elasticity allows them to store and release strain energy, which governs their post-impact velocities.

Given Data / Assumptions:

• Elastic bodies with nonzero contact compliance.
• Short collision duration; external forces like weight are negligible during impact.
• Coefficient of restitution e ≤ 1; for perfectly elastic, e = 1.

Concept / Approach:
The impact has two stages: compression (bodies deform, relative approach decreases) and restitution (bodies recover shape, relative separation increases). At the instant of maximum compression, relative velocity at the contact becomes zero; then restitution begins.

Step-by-Step Description:

Verification / Alternative check:
Newton’s impact law relates separation and approach speeds: v_separation = e * v_approach. For e close to 1, recovery is nearly complete, matching the described behavior.

Why Other Options Are Wrong:
Taken individually, (a) can be misread; however, together the options describe the full cycle (deform, pause at max compression, recover). Hence 'All of the above' best captures the correct sequence.

Common Pitfalls:
Assuming perfectly rigid contact (no deformation); confusing zero relative speed at maximum compression with zero absolute speed in every frame.

Final Answer:
All of the above — the deformation and recovery phases occur in elastic collisions, with a momentary stop at peak compression in the contact frame.