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title: "In a laboratory investigation, two small spheres of identical mass \\(m\\) are projected horizontally at the same speed \\(v_0\\) toward identical, stationary target blocks of mass \\(M\\) on a frictionless horizontal floor. Sphere 1 rebounds horizontally after an elastic collision, while Sphere 2 collides inelastically and adheres to its block. Sensors record that the block struck by Sphere 1 attains a greater final speed than the block struck by Sphere 2. Which of the following explanations best accounts for this observation?"
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url: "https://nerd-notes.com/ubq/124067/"
date_modified: "2026-09-28T13:30:20+00:00"
---

# In a laboratory investigation, two small spheres of identical mass \(m\) are projected horizontally at the same speed \(v_0\) toward identical, stationary target blocks of mass \(M\) on a frictionless horizontal floor. Sphere 1 rebounds horizontally after an elastic collision, while Sphere 2 collides inelastically and adheres to its block. Sensors record that the block struck by Sphere 1 attains a greater final speed than the block struck by Sphere 2. Which of the following explanations best accounts for this observation?

In a laboratory investigation, two small spheres of identical mass \(m\) are projected horizontally at the same speed \(v_0\) toward identical, stationary target blocks of mass \(M\) on a frictionless horizontal floor. Sphere 1 rebounds horizontally after an elastic collision, while Sphere 2 collides inelastically and adheres to its block. Sensors record that the block struck by Sphere 1 attains a greater final speed than the block struck by Sphere 2. Which of the following explanations best accounts for this observation?

![A grayscale diagram showing two collision scenarios labeled Case 1 and Case 2, stacked vertically on a horizontal frictionless surface represented by a solid horizontal line for each case. In Case 1, a small solid disk of mass labeled m moves to the right with an arrow labeled v_0 toward a stationary rectangular block labeled M; a dashed horizontal arrow pointing left indicates rebound away from the block. In Case 2, an identical disk of mass labeled m moves to the right with an arrow labeled v_0 toward an identical stationary rectangular block labeled M, coming to rest attached to the front face of the block. No other labels, lines, text, or axes appear.](https://nerd-notes.com/wp-content/uploads/ubq-frq-generated/stem-fig-1-1790602219-bTdyli.jpg)

- **A.** Reversing the sphere's velocity requires a momentum change whose magnitude exceeds the sphere's initial forward momentum, meaning the block must exert a greater backward impulse and consequently receives an equal-magnitude forward impulse from the rebounding sphere.
- **B.** The elastic collision conserves mechanical energy throughout the interaction, enabling maximum translational work to be done on the block, whereas the inelastic collision dissipates kinetic energy into microscopic deformation that cannot be converted into bulk motion.
- **C.** The rigid impact of the elastic collision produces a substantially higher peak normal force over an extremely brief contact duration, allowing the block to overcome its static inertia far more effectively than under the gradual deceleration of the adhering sphere.
- **D.** Embedding into the block increases the system's total inertial mass without adding external momentum, which mathematically reduces the final velocity compared to an elastic impact where the sphere's original forward momentum is delivered exclusively to the unmodified block.

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